Binding of Isaac: Rebirth Wiki

Guppy's Hair Ball is an unlockable passive item.


  • Spawns a hairball familiar that loosely follows behind Isaac, blocks shots, and can be swung like a flail to damage enemies.
    • The ball deals 5 damage per tick, but grows, increasing damage by 2 each time it kills an enemy — up to 5 times for a maximum of 13 damage. The damage it deals per tick (each half-second) is (level × 2) + 3.
    • The hairball level decreases upon entering a new floor: if level 2, it reverts to level 1. If level 3 or 4, it reverts to level 2. If level 5, it reverts to level 3.
  • This item belongs to the Guppy set. Collecting three items from this set will transform Isaac into Guppy.


  • The hairball's hitbox is the same size regardless of level.
  • Removed in Afterbirth † / Re-added in RepentanceIf Isaac has transformed into Guppy Guppy, Guppy's Hair Ball spawns Blue Flies when it deals damage.
  • If Blindfolded, the ball occasionally spawns a Blue Fly while it's damaging an enemy.

In-game Footage[]


  • This item is used in Cat Got Your Tongue (challenge #8).
  • The function and flavor text of this item might reference the idioms "no room to swing a cat" and "can't swing a dead cat without hitting...".
  • In the original The Binding of Isaac, Guppy's Hairball did not count towards the Guppy transformation.


Bug Bug! Added in Afterbirth / Removed in Afterbirth † Killing the Hush Flies that Hush spawns does not increase the hairball's level.