Not to be confused with the Mulligan monster
A blue fly with a blue heart above it.
Regardless of how many Flies are spawned, no more than five will follow Isaac into the next room.
It is not possible to spawn two Flies per hit while Guppy.
- Soy Milk - The high fire rate and low damage can allow massive numbers of flies to spawn by continuously attacking a single enemy.
- Inner Eye and Mutant Spider - Can spawn multiple Flies with one attack.
- Technology 2 - Has a much higher chance of spawning Flies, due to Technology 2's high fire rate.
- This item's name and effect was based on the enemy of the same name.