A Mulliboom is another alternate form of the Mulligan. It was added in the Wrath of the Lamb DLC for the original game and is commonly found in the Cellar, occasionally in the Catacombs and rarely in Necropolis.
Mullibooms have a bomb wedged into the right side of their head and cry blood rather than actual tears. Instead of avoiding the player like their other variants, they will charge at Isaac and explode on contact, dealing 1 half heart of damage. They also explode immediately if they are killed, similar to Boom Flies. Make sure to keep a safe distance when delivering the final shot, and consider killing them next to a wall that might be adjacent to the Secret Room.
- Originally, explosions from Mullibooms inflicted one full heart of damage. After many complaints about layouts where avoiding damage seemed impossible (which on the Basement often resulted in frustrating deaths), Edmund reduced their damage to 1/2 heart. This makes their explosions the only kind that does not inflict a full heart of damage.
- In the original game, Mullibooms' eyes are smaller. In Rebirth, however, their eyes are larger, compared to the Mulligans.