Please post as many as you can so the creators can try to fix some. Also, please remove any fixed bugs/glitches, or edit them to correspond with the current patch.
When the Binding of Isaac game is run on a slower/older machine, its performance may suffer from a dreadful bug: the game somewhat slows down at some moments but still remembers the keys pressed from that moment on. It then executes the keys with large delays compared to when they were originally pressed, while all the game content runs at somewhat faster speed than the keys are executed at. This can completely ruin a game session essentially killing the game character or causing a lot of unintented damage. To somewhat avoid this dreadful bug make sure you play the game on 800x600 fullscreen mode, small window and lowest details setting. To get rid of it for good: after running the game, press Ctrl+Alt+Del to invoke Windows Task Manager, select Processes tab, find Isaac.exe process and right-click it. Choose Set Priority > below normal. Albeit pretty much counter-intuitive, this actually decreases the priority of the game engine process which allows for faster processing of key presses by Flash. Fix confirmed for WotL v1.48 and the original BoI.
If you leave a challenge room (by teleporting out) after the music started (by having taken the treasure), the challenge music won't stop until the point where it would loop. Probably related to at what point the music is programmed to loop.
Persisted pre-DLC as well.
When fighting a boss in the Depths/Necropolis during a Curse of the Labyrinth, the song used in the battle against Mom will play, regardless of whether or not the boss is Mom. The same thing happens with the first boss before Mom's Heart on The Womb XL/Utero XL
Alternative chapters will play the new boss music, regardless of whether the boss fought is old or new (old bosses can still be fought on alternative XL floors). Fighting Krampus will also result in getting the new boss music if he is fought on an alternative floor. (intentional? Needs confirmation whether fixed in v1.1)
On the Character Selection Screen, if you use Arrow Keys on the Keyboard to switch between characters, no clicking sound will be played.
Getting killed can cause the music for a room/floor to reset
No sound effect for the Monstro's Tooth item.
If you die with no heart containers (either as ??? normally or anyone else by health-down and/or deals with the devil) "Hereafter" doesn't play.
Using Mom's Pad against a Fat Fly may cause the fly to freeze and become invincible through the items duration, in which case can only receive damage by any other means except the player's tears.
Freezing an Eternal Fly with Mom's Contacts or Mom's Bra, and destroying the poop or monster it's orbiting while it's still frozen makes the fly permanently frozen until you leave the room (unless you shoot it, which will move it into a corner).
As of 1.2, Tinted Rocks often drop 1 soul heart instead of 2, same with red chests.
As of 1.333, If you have Bob's Rotten Head as a Space-bar item, your chance of getting rewards by playing Fortune Telling Machines is greatly increased. Bob's Rotten Head may have replaced the role of Lucky Foot or Lucky Toe due to a bug in programming, or this may be intentional.
Having the Polaroid and at least one heart container lets you use Blood Donation Machines infinitely or until it blows up. Use all of your red hearts on the Blood Bank and for whatever reason, the Blood Bank heals half a red heart while you are invincible with the Polaroid.
Picking up The Joker Tarot Cards Card in The Chest may cause the game to freeze, then make you stuck in the item pick up frame while (most) of the items in the game scroll repeatedly above your head.
Happens with more items at more locations.
??? dies if he has only an eternal heart.
Having The Polaroid and beating Mom can result in two Polaroids. (V1.4)
Upon dying with Ankh and Dead Cat or 1-UP as any character other than ??? will result in you spawning as ???. Upon a second death, you will respawn with red hearts, but ???'s skin.
If playing as Eve, defeating The Fallen can still spawn Whore of Babylon. This does not appear to have any effect.
Dr. Fetus combined with Mr. Mega causes no damage to Pride (or Super Pride); you must use normal bombs or your activated item in order to kill Pride at that point.
Sometimes the game freezes while using a fortune teller machine.
If you have an item such as The Candle or Notched Axe, pressing space and not using the said item in a room full of Pills, Tarot Cards, etc., you can pick up the Pills without stopping to show the "pickup" animation. (Confirm?)
Upon blowing up Goblins and/or Gazing Goblin(s), they will always go to the stunned/goo form. If they return to their normal form, they can walk through bombs instead of being held up by them. Thus, making Dr. Fetus a very easy way to get killed when fighting Goblins and Gazing Goblins. (v1.48)
A bug where all rooms get empty(note there no blast marks on the floor for the machines to be exploded)
A bug where all rooms get emty(note the shop door got replaced by a boss room door)
A bug where all rooms get empty(note there's no hanged man in the shop,and the door was replaced by a boss room door)
A bug where all rooms get empty(note there is no boss or trapdoor)
If you try skipping the cutscene between levels in the same moment it starts,and the next level has the curse of he labirynth,all the rooms will be empty,and the shop door will have the apearence of a boss room.
If you unlock the devil room in the Womb/Utero 2 and travel to Sheol before unlocking ???, you will unlock the next Two Endings Automatically (e.g. if you have 5 ending so far, it will unlock 6 AND 7) as well as Ending 11 which it will play once you have defeated Satan, providing you do. If you fail to defeat Satan, you will be unable to unlock more endings by beating Womb/Utero 2 on future playthroughs.
When Defeating Moms Heart for the first few times, in the secrets screen, it will show the latest secret (e.g. a noose) twice, side by side.
As of version 1.45, there are 98/97 secrets to unlock. Getting 200 Mom kills does not unlock a secret and merely replaces the title screen; however, Platinum God overrides this title screen. Therefore, if you have 98 secrets already unlocked, then it's a waste of time trying to get 200 Mom kills.
As of version 1.45: Any process that erases so.sol (achievements fix, anti-virus or spyware software targeting so.sol, using Steam's Cloud storage), will result in 94/97 secrets being unlocked if you thought you had completed every unlock, including Platinum God (which now works again).
The four missing are as follows: Samson's Lock, Eve's Birds Foot, the Left Hand, and Cain's Eye. Eve's and ???'s in-game secrets are still reversed. So, if you had everything else from before, don't waste your time trying an Eve run again; play with ??? instead to unlock Eve's Birds Foot.
These 4 secrets will now stay unlocked as long as so.sol isn't erased.
Do NOT attempt to play the game on multiple computers using the same save file via Steam's cloud saving. The above 4 secrets will get erased if doing so and will need to be unlocked AGAIN. Unless the save files were backed up previously, ALL your computers will have the above 4 missing again.
Make sure your anti-virus or anti-spyware software leaves so.sol alone.
Be prepared to get these 4 achievements again if using the achievements fix of erasing so.sol.
Beating the Chest with Cain, Judas, Eve, ??? and Samson causes the incorrect achievement to unlock on Steam. Isaac and Maggy's achievements unlock correctly.
In-game achievement unlocks may randomly disappear.
Having Depths XL and killing the first boss before entering the Item rooms give you Samson, after that you still can get the items from the item rooms and then kill Mom.
The problem here is that for the XL levels, the first boss is also "tagged" the same as the second boss. This means that for any clear conditions, only the first boss needs to be killed.
Sometimes when unlocking secrets / achievements no notification will pop up during the gameplay. The number in the collections will increase however there will be no picture showing the unlock
This happens even without the Wrath of the Lamb extension.
If this bug happens early enough, it will result in things like Ending Cinematics, or the 10th challenge not being unlocked when you otherwise would have gotten the notification.
If playing the steam version, exiting and re-entering the game may award the missing steam achievements. However, there will still be no in-game pop-up informing you of the secrets unlocked.
Even though no pop up will be shown, the item can still be obtained normally (ie. even if no pop up is shown for Blood Rights, it can still be found.)
Whilst not a true fix, a temporary solution has been outlined by a couple of kind users on the Steam forums.
If you remove (back it up!) the secrets file from your Flash directory then run the game, it will regenerate it from your save data. In addition to adding your missing secrets to the secrets page, from this point on, further unlocks will be announced and unlocked as per usual! Seemingly the root bug is fixed, its just there's no script in game to repair all the borked files of early buyers of the game and/or expansion.
The secrets file is found here: [User]/AppData/Roaming/Macromedia/Flash Player/#SharedObjects/[GibberishString]/localhost/so.sol
A trivial side-effect to the above fix is that the order of your previous unlocks will lost and overwritten by a default order (ie: The order will become Cain, Judas, The Womb etc, instead of the typical Radioactive Spider, Spelunky etc. order).
Some of the secrets might be missing when regenerating the so.sol file from serial.txt, especially the 8 latest secrets (confirmed Samson's Lock, Eve's Birds foot, and the Left Hand in my case -ChanXing)
Clearing the Cathedral will not unlock Ending #12 in some instances, although it will display it after clearing the game.
Fixed as of v1.3? (Need confirmation)
The Counter for the Secrets goes up and you can find the unlocked secrets in-game, but you neither don't get Pop-ups for the Unlock, nor can view them in the Stats.
In some cases, the secrets counter fails to increment and secret unlock pop-ups fail to display, but the items are still unlocked.
Challenge #10 "The Purist" as well as End 12 might not unlock after beating the Cathedral (workaround here: http://www.youtube.com/watch?v=7-lc83CcvqQ). Fixed as of current versions.
The 1.15 update re-locked Ending 12 and "The Purist" for many individuals, and renders them unable to be unlocked again.
It seems that if achievements and secrets notifications start working properly, the ending #12 and the Challenge #10 remain locked.
Still in v1.2
Able to achieve Platinum God without completing Challenge #10 or obtaining Daddy's Love, Ghost Baby worked in its place.
When doing a challenge, dying with Ankh and turning into ??? makes the challenge impossible and allows you to continue to Sheol/Cathedral after killing Mom.
Secrets unlocked after beating mom/mom's heart/etc for cutscenes unlock during the cutscene, so only the sound is heard. After unlock, they won't pop up at the menu like usual, but they will show in the secrets section.
The Left Hand does not remain unlocked for some people (may be due to CCleaner removing poorly-implemented save data, needs further verification).
When you unlock Cain's Eye, a duplicate Cain's Eye page replaces the "You unlocked Magdalene" page in the found secrets. This fixes itself after the game is closed and reopened.
I got hit into this middle of a room by a spider...
Teleporting to the I am error room while in the chest forces you to quit. (Empty room with no exits.)
Using The Moon may force you to exit the secret room to an isolated area. With no doors. This can also happen when teleporting to a random room with telepills (found when under the labyrinth curse).
Also, secret rooms in XL levels can be naturally connected to isolated rooms. You can go from the secret room to the isolated room (with a bomb), but can't go back if you don't have any bomb left. You just get stuck. (be careful even the boss room can be cut off from your start point Curse of the Labyrinth is your friend till this gets fixed)
Secret rooms in XL levels often are furnished like regular rooms. (Also may contain a random Boss encounter [Blow open room, Larry Jr. is inside])
Both this bug and the above (Secret Rooms leading to isolated areas cut off from the rest of the floor) are demonstrated in the first five minutes of this video.
In the Arcade room, you can re-enter it multiple times to change the slot machine to a Fortune Telling machine.
Exiting the Curse room while flying deals damage unlike entering it while flying.
v1.3 - I got the x-ray vision in The Chest, and a crack in the wall appeared in a room, which normally leads into a secret room. I couldn't go through the crack (nothing happened as if the crack wasn't there), the same thing happened from another side of the map piece where the secret room is/should be.
v1.3 - In The Chest if you teleport into the Secret Room and are unable to blow up the Secret Room entrance you may be unable to escape, ending your run. More information on The Chest page.
The secret , error, and devil/angel rooms on the chest level cannot have their entrances opened via explosions (bombs, rockets, etc). Teleporting into these rooms on the chest level without a means to teleport out will leave the player with no means to exit and end the run.
v1.4 - Secret Rooms now act like Super Secret Rooms. They now seem to appear only touching one other room, as opposed to appearering between two or three.
(one experience) There was a bug on the second floor during the meatboy challenge, where I had 2 bosses Peep, and Pestilence. When I entered the first bosses room it had an open 2nd boss door. I went in and beat Peep, no trapdoor apeared I went back to the first boss and Pestilence was gone, with no trap door, had to kill Isaac. Other items I had were Box, Spirit of the night, 2 extra cubes of meat, the Tick, and a 9 Volt with no item to charge. No known reason if there is one edit this.
As of 1.45 you can not find the top secret room at all(fixed in 1.48)
In the Arena sometimes you get 2 lots of bosses at once instead of 1.
During some boss fights if you stay at the enterance the boss may push you out of the room.
As of 1.4, the attempt to create a Womb XL / Utero XL Floor often leads to a game crash on weaker computers (especially 32-bit systems). It may also cause the game to spawn a map so big, that the minimap goes through the borders of the BoI Window, if the Floor succeeds to generate (happened on my 64-bit Laptop System). Having random gamecrashes at a ~90% rate when my older computer tries to generate an XL Floor for the 4th chapter is a very anti-climactic end to a lot of good runs.
v1.48 - I was fighting Fistula in the first wave of a challenge room I entered in the Womb 2. After defeating Fistula, Little C.H.A.D. attempted to drop a half-heart, freezing my game.
In 1.48, if you kill Isaac with the Polaroid, you can walk into the chest to enter the Chest world. If you tag the chest (beginning the fade to white) and then run out of the room, the graphics change to the Chest but you remain stuck on the Cathedral, thus making it impossible to complete the run.
1.48 - If you spawn a regular fly with the Slot Machine or Portable Slot Machine, leave the room, and come back, the room will have reset.[1] [2]
When entering a room with any kind of Boils in it, they will spawn at their full size and go back to their small size right after.
Whenever there are Clots in a room, all enemy projectiles will flash black like Clot's.
When Vis shoots his beam, damage hitbox and sound will appear before animation. This can be easily proven by getting to half of a heart and lining up with Vis. When he shoots, you die and hear beam sound, but no beam animation will be present on screen.
Small Spider enemies are not blocked by bombs and moving bombs (pushed or Fetus in a Jar) pass through them.
Buttlickers can sometimes get stuck in a wall and become unkillable without spectral shots or wide-range bombs, possibly forcing a reset if the player cannot bomb or teleport out.
Enemies will get stuck in doorways
Ground-bound enemies that can move diagonally (including Keepers) will sometimes "squeeze" through a corner created by two obstacles (pits or rocks), even though they can't normally travel over them.
The Larry Jr.s spawned in the boss challenge room look like they only have one segment besides the head, but act like they have 2. In other words, they have two overlapping "tails".
v1.33 - Brains sometimes stay stationary.A stationary brain.
Found with Cain in The Depths I with the Curse of Darkness.
When using Gamekid or My Little Unicorn, the Hangers do not take any damage. ( This may be intentional)
When using Mom's Bra while fighting a blue champion Gurdy Jr as a boss (two Gurdy Jrs at once), and killing one of them before the end of the effect, the remaining Gurdy Jr will appear to flashing at the corners of the room, while actualy he is simply moving really fast through the room (so fast it doesn't damage you) . it will come back to normal after a while.
Attacking Mom's heart/It Lives! with the candle while it is hiding damages it. When it is left with a quarter of it's health left, it will not come down until you defeat all other enemies in the room.
If you defeat a boss and kill yourself with a bomb(?)(and have "dead cat")you will fight the boss again.proof link
Existed pre-DLC.
The VS Boss screens are extremely glitched in general, as there are instances of showing one boss yet having you fight an entirely separate boss altogether.
Sometimes on XL versions of the Caves and the Catacombs, Pestilence will appear on the first VS. screen but a completely different boss will be fought but will still drop a Cube of Meat. The second boss fight will be against Pestilence but the second VS. screen will show another boss that is neither the first boss fought nor Pestilence. Upon defeat Pestilence will not drop a Cube of Meat. Can also happen with Famine on Cellar XL.
If you kill Mom while neither her foot nor its shadow is visible, or if you kill Satan while one of his feet is "hidden" in this fashion, you will take one heart of damage as if you were stomped the moment the boss died. If this kills you, Isaac will say you were killed by a bomb.Sheol Death Animation Causing Bomb Damage
On an XL floor, if you defeat a normal boss, don't pick up the item, and proceed to fight one of the Four Horsemen as a second boss, returning to the first boss room and re-rolling the first boss's item (with the d6) will always result in a second Cube of Meat (confirmed in 1.15).
In some rare cases in a boss fight you can lose all your hearts and instantly die with a kill screen with nothing on it.
"The Fallen" Boss tends to be stuck within his Chasing Charge Attack. Planting Bombs on his way and damaging him with those Bombs unsticks him.
Gurdy may sometimes act like its champion variant without any colour change. (Unconfirmed)
Fighting any boss and having Cursed Skull and you kill the boss right when your life goes down to a half heart, and you get teleported but the boss remains dead but no there is still no passage to next level.
Sometimes Larry Jr will get stuck behind his poop rather than "eating" through it.
Larry Jr. can sometimes spawn poop in the walls or rocks.
When you fight fistula, sometimes half of it won't spawn chargers when the last bit is destroyed (same with bomb flies on the champion version). [Occurs because the game will not spawn enemies in rocks or over pits, probably to keep rooms from being unbeatable. Occurring with the Fistula variant that spawns bomb flies is likely an oversight.]
When Pin goes underground after shooting a green bomb, you can still hit him.
Using The Candle against War when he is using his attack in the air to randomly drop troll bombs will damage him. If his health reaches half in mid-air, he will not return to the screen and the player will be stuck. (Similar to the off-screen kill glitch with War and Bob's rotten head.)
It may still be possible to damage him with the candle, even if he isn't on the screen. Just look out for a spot where you can see his life decrease when you shoot the candle.
Also happens when War gets damaged by Bad Gas.
In the Satan battle, getting hit by the Fallen will often not damage you.
The Fallen sometimes becomes immune to damage after the split.
For some players, the first harbinger in any game will always be Famine in every play-through.
This is probably due to Famine being the only Harbringer that spawns in the basement/cellar. Aside from the Headless Horseman, the harbringers generally follow the spawn order of Famine/Pestilence/War/Death, with the later ones appearing further down in the level order.
If War starts a charge attack while offscreen, he will only go across the room twice. If Conquest does the same, no clones will join him, and he will stop before reaching the other side of the room.
Famine may have a similar problem, but this is unconfirmed.
Sometimes, one or both pieces left after Envy splits are those of Super Envy; they are blue, will split into three if they're big enough, and can drop Forever Alone if killed last. (This may not be a bug.)
v1.33 - Killing Mom's Heart with The Bible immediately after going into the room kills the heart, but the boss health label stays stuck on the HUD.Glitched health bar after killing Mom's Heart.
Using any form of teleportation (The Teleport! item displayed in the picture) while touching a boss chest on the same frame of animation causes the game to glitch out into an unwinnable level called "The Chest" that has the same layout as the level you have just killed the boss, albeit with a different wall. Performed using ??? in The Citadel. (Glitch found by Lizardheart)
If killed by one of Isaac's beams from heaven, the death letter will show a picture of a horseman, because the game registers you as having been killed by one of Conquest's attacks.
v1.4 - If you enter a boss battle against Pestilence, there will be always a puke bomb that he will fire at you right at the start, without him doing his spitting animation.
Brimstone charges normally in any room that has no enemies, but in battle it releases small squirts that deal about 45% of it's original damage.
This is due to the player pressing fire too quickly. If you press fire before the brimstone animation finishes, you will cancel it, rendering any cancelled animation frames completely damageless.
Using "Best Friend" on "Fallen" in causes you to die right away, and death note says died from Isaac (Possibly not a bug)
This also occurs when fighting The Bloat.
During the Satan fight, Satan's statue may act as an X-rock (has a chance to spawn soul hearts/keys/bombs/golden chests when damaged by an explosion.) It is also possible to be forced to exit the room when hit by his third form near the door. Existed pre-DLC.
When the Green champion version of Larry Jr. fires a shot downwards, his head turns into an upward-facing segment of The Hollow. (V1.48, unknown if in earlier versions)
If you kill Satan while using Moms Pad, the game will become stuck File:Error Sheol.pngSheol Error Moms Padmaking winning impossible
When in a room with two horsemen of the apocalypse that charge, i.e. War and Famine in the Cathedral level, one can push the other completely out of the room temporarily, however the horseman that was pushed will go back into the room moments after
In Challenge #10 "The Purist", if you find an Error Room or use We Need To Go Deeper in The Womb/Utero II or XL, you can enter SheThe Conquest/War Glitch in Necropolis I.
ol instead of the Cathedral. If this happens, killing Satan will count as clearing the challenge.
In Challenge #6, If you play as Judas(Learn how in the challenges section) and use a Book of Revelations in Necropolis I, Going into the boss room will show the intro of War, but will instead be Conquest (who is not supposed to be in depths/necropolis). Conquest will drop the Cube of Meat item(the item war usually drops) instead of dropping a white pony, and it will not count as a kill to conquest.
(Only in WOTL DLC as of v1.48) On rare occassions, in Challenges #3 "Large Marge" and #9 "Isaac Was Good Today", if you pass into the room, Depths I, before entering, you will go through the usual transition from room to room. TBOI will be black for about 15-60 seconds. Then, the room transition will go through again. But only this time, in black and white, and with nothing going on in Isaac's thinking bubble. Afterwards, (about 10 seconds) the same thing will happen. Then you will go into Depths I. Afterwards, gameplay is normal.
After defeating It Lives! for the second time on a run of challenge #6 The Doctor's Revenge, a chest may appear instead of the beam of light to the Cathedral. However, the trapdoor to Sheol will still appear along with it. Entering this chest doesn't go to the Cathedral, but instead skips to the credits, with no special ending before it. This does not occur when completing a run without playing said challenge.
Using a Forget-Me-Now in the Large Marge challenge does strange things. (It regenerates the level, but with a new graphical set - this leads to strange things like facing Mom in the Womb and Mom's Heart in Sheol)
Bosses will be as if the level had been regenerated normally, but the graphical set and in-between levels will act as though you were one stage deeper. Monsters may appear by either parameter. For example, a level that should be the Depths will have the appearance of the Womb, but monsters from either level may appear.
This bug appears to make the challenge unwinnable; Mom appears in the first of the two boss rooms rather than the second, and when defeated the four doors explode as normal, but the challenge does not register as cleared, leaving you trapped unless you have a teleportation item. Using it may allow you to proceed to the next boss room, but this remains untested.
Stats window can sometimes glitch out and show false stats if equipped with the DLC. Typically this manifests as not acknowledging the effect of upgrades.
F.Hopper and Scolex art in the credits are bugged and seem to flicker between Leaping Spider and Pin, respectively. Fixed as of 1.4
An example of the glitched Issac that spawns with The Rock.
The info plate that displays on the bottom right corner every time you pick up an object sometimes doesn't display or just the half of it is displayed.
In the second Necropolis and Utero stages, sometimes the lower left corner of the screen that displays the stage name doesn't have a number (or it doesn't display "XL" if Curse of the Labyrinth is activated).
When picking up certain items as Samson, such as Jesus Juice, he will lose his hair.
The Mask of Infamy has no health bar. Edmund McMillen has stated that this is intentional because "the thing inside the mask is not living", but it may actually be due to technical limitations (i.e. requiring a second health bar for the mask, which would call for a lot of unnecessary recoding).
TNT barrels, rocks, and poop sometimes appear inside of walls.
Trinkets have the same icon on the map as tarot cards. (Intentional?)
When having a tarot card surrounded by trinkets, while having "The Tick" which makes you unable to pick up other trinkets, picking up the tarot card shows the animation of you picking up a trinket, when you're actually picking up the tarot card
Even if the Devil Room in the boss room for Mom's Heart/It Lives is replaced with an Angel Room, it will still contain a trapdoor to Sheol.The tarot card-trinket bug
When Cain gets toothpicks both eyes get propped open instead of just his good eye; his shots are not affected.
When shooting a fully charged Chocolate Milk shot while facing sideways, Cain's eyepatch will move to a different part of his face, then move back to its original place.
??? has color mismatch issues with items such as the Holy Grail much like he has with the Growth Hormones.
Maggy is named "Magdalene" on the Character Selection Screen, but when you encounter Mini-Bosses, it says "Magdalena" instead. (Example: Magdalena vs. Gluttony)
This happened before the DLC as well
When the Tarot card 'The Devil' is used on War, his body turns invisible, and he cannot be seen. He still attacks the player. (Found in the meat challenge with labyrinth)
Triachnid and Daddy Long Legs do not have death animations.
When entering different rooms during the Curse of Darkness, the map will briefly show a heart and revert back.
If the Red Patch is activated with a flying item other than Transcendence, said flying item's visual effect is not visible and Isaac apears as a floating head.
The appearance of the Super SMB Fan cannot be overridden by other appearance changing items that completely change the look of the character, such as the Whore of Babylon and IPECAC.
This may be intentional however.
"A Lump Of Coal", however, entirely overrides the face.
Killing Scolex with bombs, IPECAC or other explosive attacks can cause the explosion animation to loop in place for an indefinite period of time. (Existed pre-DLC as well.)
Upon acquiring certain familiars (Bag of Pennies, Little C.H.A.D., possibly more), Brother Bobby will appear. He will disappear when you exit the room.
Some familiars can replace others with Brother Bobby unless Brother Bobby is actually found (permanent) or the Holy Water that caused the change is spilled (temporary).
A pill may show the positive animation despite having a negative effect, most notably the Luck Down pill.
When entering in a new floor, if the secret room is adjecent to the spawn room, it will appear briefly then disappear.
Various graphical glitches with Mr. Maw, including, invisible heads, bodies replacing heads
Getting Little Gish (Item Room, not the Boss.) and then The Relic makes Little Gish turn into Brother Bobby. (V.1.3 only?)
When picking up Tear increasing items, the tear stat (and range stats occassionally) do not visibly increase, and on rarer occasions, do not increase the stat at all
Sometimes, stat-boosting items appear to increase the "wrong" stat, e.g. the Pentagram resulting in a Tears upgrade. This may or may not be true in actual gameplay.
When fighting Conquest in The Depths (as a replacement for War), you will receive the standard War intro graphic.
The health bar found when fighting War and Famine simultaneously (in The Chest) only tracks War's health.
Sometimes when you are in the holy room familiars (that attack for you) will turn into brother bobby (cannot
The chest from Ending 12 in the Jet-Black "corner"
remember what familiar I had specifically, maybe little gish or sister maggy). After you leave the holy room, however, they turn back into the original familiar.
If Scolex fires a bomb that collides with a poison tear (and maybe with other kinds of tears), it is frozen in mid-explosion and becomes harmless. The "cloud" it leaves behind can be pushed around like a regular bomb.
In the credits, Sloth still has the same appearance as a Globin enemy; he's red instead of green. (This is the case even without the DLC, and it may be a joke related to Sloth's "lazy" design.)
While fighting Pin, he may randomly regain all of his health. The layer of ground he creates when burrowing will disappear, however.
During Ending 12, when it shows the chest in the corner, the walls are completely black. (May not be a bug.)
Sometimes, when a blood beam (like the one a vis shoots) is on screen, Robo-Baby fires a laser similar to the lasers fired when Polyphemus is collected with Technology. This does no increased damage.
Super Sloth sometimes appears as the normal Sloth.
Technology 2. (The sound bug happens even without Brimstone.) (In combination with some other items like Brimstone, Bloody Lust and others may cause Brimstone to be bugged, preventing it from being fired but dealing mass damage, killing It Lives in about three seconds. Picture below.)
Technology 2 + Mom's Knife: Technology 2's laser fires as normal but does no damage.
Technology 2 + Epic Fetus: Tech 2's laser fires briefly, before the bomb crosshair starts flashing. The laser does normal damage. The crosshair is also being delayed a bit before it appears.
Acquiring Ipecac first, and then Technology 2 will give you both attacks. The reverse will max your attack stat, but will not yield the Ipecac attack.
Shots don't penetrate rocks when using Technology 2 and Ouija Board, unless paired with Technology 1.
Cannot throw Bob's Rotten Head when equipped with Technology 2.
Technology 2 + Number One (Cain only): Still doesn't fire Number One tears, even though they come from the lower part of his body.
The Candle will not fire with Technology 2.
When using the 3 Dollar bill in conjunction with another tear effect, there is a chance the 3 Dollar Bill will override the other effect instead of complementing it.
The Rainbow Baby might get buggy and gets replaced by Brother Bobby through a fight, but switches back after it.
When collecting a Harlequin Baby while holding a Rainbow Baby, the Rainbow Baby will become a second Harlequin Baby
Holy Water may cause the next tear-firing familiar in line to revert to Brother Bobby until the Holy Water effect is activated.
Having Robo Baby and Little Steve causes Little Steve's shots not to fire and show random purple splotches on the walls in random directions (as if Little Steve shot there) during a fight, but after he shoots normally.
If you obtain Isaac's head, Little Steve, Abel, and then Sister Maggie familiars, Little Steve will turn into a second Abel.
The blue flies created from using Guppy's Head sometimes glitch out and get stuck in one place, and the animation stops.
Sacred Heart's description says "Space to Use" but isn't a use item and doesn't replace your current use item.
If you acquire Brimstone after picking up Technology 1 and then Ipecac you will be completely unable to fire no matter how long you charge Brimstone. (May be the same as the bug listed below).
When using Ipecac, Lump of Coal, Sacred Heart (might happen with other homing effects, not confirmed) and 3 Dollar Bill, there's a chance that 3 Dollar Bill will activate the effect of My Reflection, making the Ipecac bullets hover over enemies gaining size and over a moderate lenght of time falling over your enemies, but if you come near the enemies the bullet will follow you and explode until hitting a wall.
Acquiring Holy Water and then the Little Steve familiar causes the holy water to "cut in line" ahead of Little Steve, forcing it to turn into a Brother Bobby. Activating the Holy Water makes Little Steve return, but only for that room.
If you pick up Brimstone while you have Ipecac, Brimstone charge time is greatly increased
If you pick up Fetus in a Jar while you have Mutant Spider, your firing speed is greatly reduced.
If you use Best Friend with Cain when you're fighting with Mom, it kills you just like using it with Fallen.
Guppy's Tail is supposedly unlocked by completing the 9 Deaths challenge, but it is possible to find it before completing the challenge.
3 Dollar Bill can give the Magnet effect.
"Doctor's Remote" / "Epic Fetus" 's Cursor is being pushed back by Fires and a "Burned" sound can be heard whenever it occurs.
Mouse-listener lags the Player Input severely when used with Doctor's Remote / Epic Fetus.
Ipecac does not interact correctly with Spectral Tears, regardless of whether you gain them before or after Ipecac. (e.g. if you are flying above a rock, shooting will blow it up in your face, damaging you)
White flies are still able to harm a player equipped with Skatole.
Liberty cap can give the compass effect temporarily.
Might be intentional.
With Epic Fetus in a Jar and Technology, the laser will fire but will not be visible.
Sometimes, Dr. Fetus bomb's hitbox doesn't work and goes through enemies.
Jesus Juice seems to only increase your damage instead of tears and range.
The Mark is bugged and will not increase damage - it will only give a single spirit heart.
Sometimes you may acquire bugged pills which end up being different color upon use rather than what it is being displayed to you.
Egg Sack (Daddy Long Legs) attacks Isaac (Boss) during the Isaac Boss Fight only once.
Bob's Rotten Head is afflicted by The Wiggle Worm and has a wavy flight when unleashed.
Bob's Rotten Head seems to be affected by My Reflection effect as well, at least when carrying the 3 Dollar Bill.
After using Mom's Bra, the Epic Fetus crosshair will be frozen as well. Bomb's will still drop onto the crosshair normally.
Picking up Mom's Knife when you already have Epic Fetus results in Mom's Knife working only in the room you picked it up in, reverting back to Epic Fetus once you leave.Timing Guppy's Paw with your last heart loss allows you to survive
When picking up the Treasure Map or Compass item, the minimap does not update until you exit the shop/room you found it in.
Picking up the @#!*% of Babylon item will immediately give you its effects, at least graphical, while you are in the room you picked it up in, regardless of whether you are actually down to half a regular heart. Leaving the room sets you back to normal.
After using Mom's Pad, Super Pooters are frozen but cannot be hit. Only after the effect wears off could they be hit and killed.
When an enemy with a guardian fly is killed while frozen, the fly stays in the white passive state and never turns red/aggressive.
When you find and use the "Puberty" pill and then find the "I Found Pills" pill (after you use Puberty) you see the text of "I Found Pills".
If you have Ipecac and enemies are against a wall (or stationary like boils), shooting with too much speed sometimes won't damage them.An example of the Eye Laser/Best Friend bug (note the one remaining spirit heart)
Laser-type hits on a deployed Best Friend can kill you instantly, even when the attacks don't hit your character. The death sequence itself is also glitched out in several ways - Best Friend shakes for a while, and then the standard death screen pops up, with Isaac as the cause of death. The rest of the screen doesn't dim out either.
Dr. Fetus and Brimstone: Brimstone will not fire.
If you have both Abel and Dead Cat, the floating cat head will move with Abel instead of following Isaac.
The '<3' (heart) item does not show its name on the collection screen when selected.
The Box item removes all walking animation when going up or down.
Holy Grail does not give ??? a blue heart when picked up.
Some items in the Angel Room will appear without being unlocked. (ex. Guardian Angel without having beaten Satan with Maggie)
Dead Sea Scrolls can possibly select Wiggle Worm, which is not an activated item. It has no effect when this occurs. Also, DSS seems unable to choose any of the WotL activated items.
More than one copy of a tricket may appear; however, it is impossible to pick up the second copy whilst holding the first, even if you have obtained Mom's Purse.
Using a Forget Me Now on the Cathedral will take you to Sheol.
Using the Candle while having Mom's Knife will let the knife float in midair allowing Isaac to move away until he throws the flame. The knife can also float outside the screen sometimes but will come back.
9-Volt sometimes may not function with Bob's Rotten Head.
After dying and becoming ??? (Blue Baby) due to the Ankh, if you aquire Dead Cat and die again you will be spawned with 1 regular heart, but the game will still recognize you as ??? and all achievments unlocked will be unlocked under ???
If you acquire Kamikaze and you hold down on the bottom wall of a room you sometimes don't get damaged.
Using Portable Slot in a Super Secret Room with the Cathedral background will result in eternal hearts dropping instead of soul / normal hearts. This is not a bug.
Using the Razor Blade while having one or an half heart will affect no image on isaacs last will.
Arena will sometimes not open, even if at full health.
Sometimes, when you try and skip the dream sequence between floors with the Spacebar, the game freezes, the screen turns black, then plays the cutscene, but the thought bubble has no animation in it and the colours turn white and pale pink. Usually happens in the cutscene before Depths 1, and on the Womb cutscenes. Sometimes doesn't carry on with the no animation white and pale pink colour but simply turns off by itself.
This whited-out-cutscene-freeze happens quite reliably when (1) generating an XL level (i.e. Challenge 3) AND (2) holding an Eternal Heart piece during the level transition.
Skipping the dream sequence is dangerous in general - it sometimes can freeze your game, to the point it will never unfreeze, and you will have to close the game by Task Manager, ending your current run and possibly loosing some progress (as TBoI saves it strangely).
You can't skip ending 13.
Having the game in a small window setting will cause item pick-ups to not have phrases (after picking up an item, there will be a blank description box of the item) (possibly not a glitch.)
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beacause i have that game and if there so many glitches i would have to be careful of all of them and my eyes looking hurt after looking at ...
