Guppy

After picking up 3 items from the following list Isaac turns into his cat Guppy.

As Guppy, Isaac gains flight, and when one of his tears or one of his familiar's tears hit an enemy, a Blue Fly spawns.

As Guppy, Isaac gains flight, and when one of his tears hit an enemy, there is a 66% chance to spawn a Blue Fly.

Activated Collectibles[]

Name	ID	Icon	Quote	Description	Quality
Guppy's Head	5.100.145		Reusable fly hive	Spawns 2-4 friendly Blue Flies that damage enemies.	2
Guppy's Paw	5.100.133		Soul converter	Converts one Red Heart Container into three Soul Hearts.	3

Name	ID	Quote	Description	Quality
Dead Cat	5.100.81	9 lives	Sets Isaac's Red Heart Containers to 1, but grants 9 extra lives. After dying, Isaac respawns with 1 Red Heart Container.	3
Guppy's Collar	5.100.212	Eternal life?	Grants a permanent 50% chance to respawn with 1/2 of a Red Heart after death.	1
Guppy's Hairball	5.100.187	Swing it	Spawns a familiar that loosely follows behind Isaac, which blocks shots can be swung like a flail to damage enemies. Grows bigger by killing enemies.	1
Guppy's Tail	5.100.134	Cursed?	Room Clear Awards have a 1/3 chance of being replaced with a Chest and a 2/9 chance being replaced with nothing.	2
Guppy's Eye	5.100.665	An eye for secrets	Shows the contents of Chests, Fire Places, Grab Bags, and Shopkeepers before they're opened/destroyed.	2

Name	ID	Icon	Quote	Description
Kid's Drawing	5.350.169		Looks familiar...	While held, counts as one of three items needed to transform into Guppy.

Technology 2 spawns flies only very rarely.
If Isaac has transformed into Guppy, Guppy's Hairball spawns Blue Flies when it deals damage.
If all the 9 extra lives have been consumed, Dead Cat is removed from Isaac's inventory. If Isaac only has three Guppy items prior to losing Dead Cat, then its disappearance will cause the Guppy transformation to be removed.

This transformation is a reference to Edmund's first cat, as seen in some of his early videos on his personal channel.^[1]
- Guppy the cat passed away in 2014.^[2]
Transforming into Guppy as The Forgotten will give him the appearance of a cat's skeleton.
The guppy item tag determines if an item counts towards the transformation, except for Kid's Drawing which seems to be hard-coded to count as a Guppy item despite not having the tag.

3. Referenced as the "One true champion" in the 22nd Ending