Binding of Isaac: Rebirth Wiki

Bob's Brain is a passive item.


  • Spawns a floating brain familiar that can be fired towards enemies as a projectile.
    • Removed in AfterbirthBob's Brain is fired directly from where Isaac is standing.
    • Added in AfterbirthBob's Brain is fired directly from where it is located in the chain of familiars behind Isaac, making aiming it slightly more difficult.
  • If it hits an enemy, it deals 3.5 damage and explodes, further damaging and poisoning monsters.
    • Removed in Repentance The explosion deals 60 damage. The poison deals double Isaac's Damage over time.
    • Added in Repentance The explosion deals 100 damage. The poison damage is dealt 4 times, inflicting Isaac's Damage per tick.
    • Added in Repentance The explosion ignores armor.
  • The explosion can hurt Isaac, dealing a full heart of damage.
    • This can make picking up the item a risky choice, as Bob's Brain will always fire, regardless of whether or not Isaac will be caught in the explosion.
  • Once it explodes, it takes a few seconds to re-appear.
  • Added in Afterbirth This item belongs to the Bob set. Collecting three items from this set will transform Isaac into Bob.


  • Bob's Brain is affected by most bomb modifiers.
  • Bob's Brain only explodes when hitting an enemy, and does not explode upon hitting a fire, poop, or wall. It can destroy poops and fires like normal shots, however.
  • Bob's Brain never launches immediately upon entering a room unless a tear-firing key is released and pressed again, or until several seconds have passed.
  • It is possible to get multiple Bob's Brains to spawn on the same floor by finding one in a Locked Chest Locked Chest and not taking it
    • Only one copy of the brains will be active at a given time, with another one firing immediately after the first has exploded or starts to return from a miss.
    • Removed in Afterbirth Multiple copies of Bob's Brain will float in the same spot in the familiar line.
    • Added in Afterbirth Each copy takes up their spot on the familiar line, but only the first one launches out. Respawning brains may end up stacking on top of each other.


  • BFFS! BFFS!: The impact damage is increased to 7 and the explosion deals an additional 25 damage.
  • Mr. Mega Mr. Mega: The explosion deals an additional Removed in Repentance85/Added in Repentance50 damage.


  • Removed in RepentanceBomber Boy Bomber Boy: No cross explosions. Damage from the explosion is halved against the initial target, but others caught in the blast take full damage.
    • Added in Repentance Explodes in a cross-shaped pattern. Damage from the main explosion deals a flat 37.5 damage, and any additional explosion deals flat 75 damage to which Bomber boy's damage reduction is not applied.
      • Bomber Boy + BFFS! BFFS!: Explosion damages are increased to 1.25x, which are 46.875/93.75 each.
      • Bomber Boy + Mr. Mega Mr. Mega: Explosion damages are increased to 1.5x, which are 56.25/112.5 each.
      • Bomber Boy + BFFS! BFFS! + Mr. Mega Mr. Mega: Explosion damages are increased to 1.75x, which are 65.625/131.25 each.
  • Added in Afterbirth †Duct Tape Duct Tape: Bob's Brain stays in place relative to Isaac until it is fired.
  • E. Coli E. Coli / Flush! Flush!: Bob's Brain will explode upon hitting an enemy that has been turned into poop.

In-game Footage[]