Question: how to get guppy binding of isaac rebirth?
Answer: Isaac's Guppy transformation from the original game. Guppy is Isaac's pet cat, and mentioned as sole heir of Isaac's findings on Isaac's Last Will. He has a total of five items related to him in the original game (6 in Rebirth) and upon collecting three (excluding Guppy's Hair Ball), will transform Isaac into Guppy.