Before Peep does an attack, he will give a signal as to what attack he's going to do.
- A spray attack that sends ten urine projectiles flying out in a radial burst pattern. This is signalled by Peep smiling and bringing his hands to his face.
- A jump that brings him crashing down on the location he last saw the player standing in. This is signalled by Peep smiling and throwing his arms wide.
- Oozing out glowing puddles of yellow creep that deal 1 heart damage if you stand in them. These go away after 5–6 seconds, and don't affect characters with flight. This is signalled by Peep frowning and slightly shrinking, along with him making a burping sound.
Additionally, at 66% and 33% health, he'll detach one of his eyeballs and set it to bouncing around the room in diagonal lines. The eyeballs cannot be damaged at all until you kill Peep himself, so don't waste your time shooting. They leave behind a purely cosmetic blood trail but do 1/2 heart of damage on touch normally and 1 if you are fighting him in The Womb. If you happen to run into Peep himself, beware that he always does a full heart of damage on touch.
The following strategies have proven to work against Peep:
- The biggest problem in dealing with Peep is the radial burst. You can dodge behind rubble piles (or hover above them if you have flight) to avoid the spray if there are any, but often you'll be facing him in an empty room. Your best option there is to stay well away on his left or right side, moving back and forth between opposite sides of the room whenever he launches. At maximum range, you should be able to dodge the burst with just a little movement up or down to put you between shots. Don't forget to watch for the eyeballs, they can sneak up on you if you're too focused on Peep.
- Because this fight requires so much dodging, items that require careful aim are best avoided. With good timing, bombs/Mr. Boom can be used to catch Peep when he lands after his jump. Spoon Bender or I The Magician can help greatly in keeping your shots more or less on target while you dodge the pee spray. Range increasing items will give you more room to maneuver; conversely, range reducing pickups like Number One or My Reflection will make your life harder in this fight. Continuous, sustained fire from maximum range is the order of the day here. His eyes are also slowed down by Skatole, making them easier to dodge.
- The Spider's Bite's slowing tears effect affect Peep in an unusual way. While slowed, Peep's jump will send him straight up into the air, then right back to where he launched from (as opposed to Peep launching and then landing at the location he last saw the player). This makes his pattern very predictable, as Peep can be kept at one spot indefinitely, with the player only occasionally needing to move to dodge the pee spray and eyeballs.
- Despite being able to jump to great heights, he can't move over rocks while airborne. This allows you to take cover behind or over rocks, but it can also mean that predicting where he lands can be tricky without following the urine trail he leaves while he's airborne.
- If II The High Priestess reduces Peep's health below 33% health before his first eye comes loose, only one will be spawned. Graphically, he will have both eyes missing, but you will only have to dodge one for the remainder of the encounter.
Both of his eyes are out right from the beginning of the fight. Otherwise, he behaves the same as the original version.
Is physically smaller and behaves like the original, but constantly leaves a urine-trail, even while in mid-air during a jump, which hurts the player if stepped on.
- Pronounced Pee-pee as a double entendre as his two sources of damage are urine and his eyes.
- Peep appears in the game's demo.
- If his eye kills you, a Boom Fly will appear on Isaac's Last Will. This is due to the fact that his eyeballs share the same AI as a Boom Fly.
- Also referred to by the less than flattering names "Slug Boy" and "Pisser" in the art booklet of the Unholy Edition.
- If his urine trail kills you, a Brain will appear on Isaac's last will.
- This is the case with all forms of creep.
- The two invincible eyeballs that detach from Peep may be a reference to Gleeok from The Legend of Zelda, a boss which would spawn two invincible heads when damaged.
- Since Peep's eyes share coding with the Boom Fly, his eyes may explode when Peep dies or even sometimes shoot six blood projectiles in the same manner of a Red Boom Fly and their movement will be slowed by Skatole.
- If you stand right in front of the boss door he will sometimes push you out of the boss room if he jumps on you.
|Basement||Larry Jr. • Monstro • The Duke of Flies • Gemini • Steven • Famine|
|Cellar||Widow • Pin • The Duke of Flies • Famine • Gurdy Jr. • The Blighted Ovum|
|The Caves||Fistula • Peep • Gurdy • Chub • C.H.A.D. • Pestilence|
|Catacombs||The Husk • The Hollow • The Blighted Ovum • The Carrion Queen • Peep • Pestilence • The Wretched • Gurdy Jr.|
|The Depths||Loki • Monstro II • Gish • War • Mom|
|Necropolis||Mask of Infamy • Daddy Long Legs • The Carrion Queen • The Bloat • Loki • War • The Wretched • Mom|
|The Womb||Scolex • Blastocyst • The Bloat • Death • Conquest • Daddy Long Legs • Triachnid • Teratoma • Mom's Heart • It Lives|
|Utero||Teratoma • The Bloat • Death • Conquest • Daddy Long Legs • Triachnid • Lokii • Mom's Heart • It Lives|
|Sheol||The Fallen • Satan|
|First to fifth and seventh level||The Fallen • Headless Horseman|