Familiars that have charged attacks will operate on similar rules to Marked: they will immediately fire at full charge, and variable-charged attacks will be released earlier the closer that King Baby is to the target.
Lil Monstro is an exception to this, still only firing when the fire button is released.
When Isaac stops firing tears, King Baby moves rapidly back towards Isaac.
This item belongs to the Conjoined set. Collecting three items from this set will transform Isaac into a three-faced version of himself.
King Baby will move back towards Isaac during Isaac's hurt animation, even if a fire button is still being held.
Abel will still reflect Isaac's movements, and not King Baby ones.
Isaac's Heart: Isaac can fire tears and leave King Baby and the heart behind, and run into a group of enemies without being damaged.
BFFS!: Increases King Baby's size. No other effect.
Duct Tape: King Baby will stay in place relative to Isaac until Isaac starts firing tears. Then King Baby will remain stationary until Isaac has stopped firing and will rapidly move back to him.
Gemini: Suture will rest near King Baby as long as there are no enemies near Isaac. When Isaac gets near enemies, Suture will rapidly snap from King Baby toward the enemy. Functionally, King Baby has no real effect on Gemini.
Visually, this can result in the umbilical between Isaac and Suture getting stretched to a long length.
Friendship Necklace: Familiars will orbit King Baby at all times instead of Isaac, even while not firing. King Baby itself is unaffected.
RC Remote: Overrides King Baby's halting; familiars will mimic Isaac's movements even while firing. King Baby's auto-targeting remains active.
King Baby references the official Binding of Isaac tarot card set, in which ??? represents the Emperor.
The Steam achievement description for unlocking King Baby says "Unlocked a new co-player baby," despite it being an item.
Before Repentance, King Baby's pickup quote was "Lord of the dead!".
King Baby's Repentance quote is a reference to Army of Darkness