Doples mirror Isaac's movements exactly. They only react when Isaac fires a tear, which they respond to by firing a large blood shot. These shots are fired at the same frequency as Isaac's tears.
The Evil Twin is an alternate version of the Dople that can be found in Sheol. It can also replace the Dople in The Womb and Utero, which will make it count as a Champion. Evil Twins have flight, and thus, cannot be killed with Spikes. However, because it has The Inner Eye, its fire speed is slowed down sharply, making shooting at angles and dodging the upgraded Dople's attacks far easier than with the normal version.
- The most efficient way to kill a Dople (besides natural hazards) is to stand on one side of the room and drop a Bomb, then to run over to the opposite side, causing the Dople to move where the lit bomb is and killing it in one hit.
- In a room with Spikes on both the top and bottom corners, it is possible to damage the Dople without damaging Isaac by standing very close to a Spike tile, but not touching it. The Dople will still take damage, while Isaac will be left unharmed.
- Damaging Orbitals such as the Cube Of Meat can allow you to easily kill Doples by standing close to them.
- If you have a large amount of Range, you can simply fire tears from one end of the room without being damaged, because the Dople's blood shots cannot reach the wall.
- If the player has a charging shot, such as Brimstone or Chocolate Milk, and a shooting familiar, like the second stage Cube Of Meat or Sister Maggy, it is also possible to defeat Dople by lining Isaac up opposite him and holding the charge; Dople will not fire until the player does, but the familiar will still fire and damage him.
- The easiest way to kill a Dople is to clear the room of all other Monsters (if any), and stand on top of it. Since it does no contact damage to Isaac, nor does it collide with him, Isaac can fire tears on top of it and deal damage without any risk. The Virus makes this even easier.
- Abel will always end up directly on top of Doples, making it effortless to hit them from complete safety.
- Isaac can obtain the same skinless texture as Doples by using the Razor Blade.
- The Dople is a reference to the game Tomb Raider, where a skinless enemy who mirrored Lara's movements had to be killed by being lured into a lava trap, similar to how Doples can be lured into spikes to be killed.
- The dark Blue champion Dople lacks the skinless texture that regular Doples have, essentially making it look like a recolored Isaac.
- Evil Twins look identical to Isaac with the The Inner Eye, The Nail and the Lord Of The Pit items.
- Sometimes, while holding Mom's Knife, the Dople will shoot in the opposite direction.
- If the player goes over a rock with flight, the Dople will walk over it, still following the players opposite movements, but he will glitchily move through it.