On use, summons Baby Plum to fight for Isaac in the current room for roughly 10 seconds.
Baby Plum will always twirl, jump, then spit blood and bounce around the room before waving goodbye and flying away.
Baby Plum does 12 contact damage per tick (24 per second), 3.5 damage per shot, and 2 damage per tick with creep (20 per second).
This item belongs to the Beelzebub set. Collecting three items from this set will transform Isaac into a giant humanoid fly.
Notes
If Isaac goes enough time (about half a minute) without hurting Baby Plum during a boss fight, she will fly away and leave behind a Plum Flute on the Boss Room pedestal.
Damage done with Suplex! does not count as hurting Baby Plum.
Damage done indirectly, like losing Black Hearts, does not count as hurting Baby Plum.
Book of Virtues: Spawns a wisp on the middle ring, resembling Baby Plum. When the Baby Plum spawned from using Plum Flute bounces diagonally around the room, all the wisps will bounce around the room and fire tears behind themselves as well. The wisps are invulnerable while bouncing around the room.
BFFS! / Hive Mind: Doubles Baby Plum's contact damage, but not projectile damage. Plum is also larger.
Car Battery: Summons two Baby Plums, the Baby Plums start out overlapped but can sometimes split up when using different attacks.
If Baby Plum is currently active when Tainted Lazarus swaps forms, Baby Plum will vanish. Once Tainted Lazarus swaps forms again, Baby plum will re-appear and continue her attacks.
If she was doing her spit attack, her and her projectiles will end up stuck in place and she will not stop attacking until the player leaves the room.
Bug!
If Baby Plum is charmed by The Siren, her animation will freeze, she will stop firing bullets, and she will only be able to deal contact damage to Isaac.
Baby Plum to fight for Isaac in the current room for roughly 10 seconds.
Beelzebub set. Collecting three items from this set will transform Isaac into a giant humanoid fly.
Suplex! does not count as hurting Baby Plum.
Black Hearts, does not count as hurting Baby Plum.
Demon Baby, 
Succubus, and 
Psy Fly does count as hurting Baby Plum.
Angelic Prism: 
Book of Virtues: Spawns a wisp on the middle ring, resembling Baby Plum. When the 
BFFS! / 
Hive Mind: Doubles 
Car Battery: Summons two Baby Plums, the Baby Plums start out overlapped but can sometimes split up when using different attacks.
Lost Cork: Affects Baby Plum's blood puddle.
Sacrificial Altar: Baby Plum can be sacrificed for free, instead of a familiar. Plum Flute can still be used as normal afterwards.
Baby-Bender: No effect.
Eraser: Plum Flute will still function normally if the boss Baby Plum is erased.
Bug!
Crawl Space or 
The Beast fight, she will not properly bounce off walls.
Tainted Lazarus swaps forms, Baby Plum will vanish. Once Tainted Lazarus swaps forms again, Baby plum will re-appear and continue her attacks.
The Siren, her animation will freeze, she will stop firing bullets, and she will only be able to deal contact damage to Isaac.
The Binding of Isaac: Rebirth
