- Spawns a familiar that bounces diagonally around the room, deals 8 damage per tick or 120 damage per second and applies a random status effect to enemies it comes in contact with. The familiar also has a chance to re-roll pickups that it passes over into other pickups, chests, or items, in an uncleared room only (with at least one enemy alive).
- Spawns a familiar that follows Isaac. Double tapping the fire button launches it forward, causing it to reroll the first monster, trinket, or pickup it hits. It respawns after clearing a room.
- If it cannot reroll an enemy (e.g. a boss), it will deal 8 damage instead.
- It can also be used to reroll trinkets into pickups.
- Pickups may also be rerolled into chests.
- GB Bug can block projectiles.
- GB Bug does more damage per second than The Peeper, with the added random status chance.
- GB Bug is able to reroll Throwable Bombs into normal consumables. After doing so, the corresponding Bomb Grimace will generate another Throwable Bomb, making it able to generate a potentially large amount of free consumables.
- The Twins: the familiar can be duplicated even if it hasn’t respawned; by constantly moving to new rooms, GB Bug can constantly respawn, allowing pickups to be rerolled indefinitely.
In Rebirth 
In Repentance 
- Before Repentance, GB Bug's pickup quote was "Game breaking bug, right away!"
- This item's in-game appearance may be a reference to "Missingno.", a famous bug occurring in the first Pokémon games.
- As Edmund confirmed on Twitter the pickup quote "Game breaking bug, right away!" is a reference to a quote by Phil Fish in Indie Game: The Movie, where he says the same words when a bug is discovered in the game "FEZ" on the first day it is being shown at PAX.
PC GZWT H4LE (First floor Treasure Room)
|The Binding of Isaac: Rebirth|
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