GB Bug is an unlockable familiar in The Binding of Isaac, added in the Afterbirth DLC.

Spawns a familiar that follows Isaac and can be launched forward by double-tapping a fire button.

The familiar will reroll the first monster, trinket or pickup it hits when launched, after which it will disappear for the rest of the room.

If it hits an enemy that cannot be rerolled (e.g. a boss), it will deal 8 damage instead.

Cannot reroll items and opened chests.

Any pickup has a 10% chance to be rerolled into a chest. Rerolling a chest has a 28% chance to stay as some kind of a chest.

This page shows the latest information as of the new Repentance+ (Online Co-op) DLC.
To see information about this item for the previous Repentance version, check this page instead.

Defeat Ultra Greed as Eden.

GB Bug can be found in the following item pools:

The following tags are applied to this item:

The following special synergies and interactions for GB Bug have been documented.

* Note that not all possible synergies and interactions are listed here.

Below is the Internal Item Description as shown in-game.
Note that some stat changes are not displayed here. Please see the main description for the full effects.

GB Bug

• Double-tap an attack button to shoot familiar
• Rerolls the first enemy, pickup, or trinket it contacts
• Respawns after clearing the room
• Abyss: x1 rerolling locust .75x Isaac's damage

• Check out the item description on the external Isaac Wiki.