Guppy's Collar is an item added to The Binding of Isaac: Rebirth. It is a pink collar with a white heart on it.
Upon pickup, gives Isaac a permanent 50% chance to respawn with half a heart upon death. The text "x1?" appears next to Isaac's health, showing the possibility of additional lives.
Will transform Isaac into Guppy if he collects two more items that belong to Guppy's set.
- RWBY 10FQ (PC) - There is Curse Room near where you spawn. Guppy's Collar is inside a Red Chest in that room.
- RJQK T8SP - 2nd Floor Devil Room inside Boss.
- H8P3 M0ML - 2nd floor Devil Room after defeating Monstro.
- 3VD1 EFNP - (3DS) Contains Guppy's Collar and Guppy's Head in a devil room.
- ZKCA 0JD3 - (PC) Contains Guppy's Collar and Dead Cat (9x? lives).
- The 50% Chance of respawning may be a reference to Schrödinger's Cat