Multidimensional Baby 
Effects
- Spawns a familiar that follows Isaac's path with a 2-second delay.
- (Added in Repentance) The delay is 0.66 seconds instead.
- When a friendly tear passes through Multidimensional Baby, the tear splits into two parallel tears that gain a 1.33x speed boost, +4 shot height, and also a visual black and white flashing effect.
Notes
- It is possible to crash the game when combining this item with rapid-fire or multi-shot laser tears.
- Duplicated tears will deal the same damage as Isaac's tears.
- If other familiars that move with a similar pattern such as (Added in Afterbirth †)
Shade have been collected before the Baby, it will follow them instead with further delay. - Standing perfectly still with the Multidimensional Baby inside of Isaac will activate its effect, as the tears will pass through it as they spawn.
- This does not work with attacks such as Brimstone.
- (Added in Repentance) This item belongs to the Conjoined set. Collecting three items from this set will transform Isaac into a three-faced version of himself.
Synergies
Brimstone: If a brimstone laser is shot through the baby, it will double the laser.
Cricket's Body/
The Parasite: Tears that pass through Multidimensional Baby will duplicate and their split tears will duplicate. Half of the tears fired through Multidimensional Baby retain The Parasite's look and the other half have the flashing appearance.- (Added in Afterbirth †)
Haemolacria: Haemolacria shots will be duplicated and more burst tears will spawn. Burst tears that pass through Multidimensional Baby will also be duplicated. - (Added in Repentance)
Papa Fly: Papa Fly will always shoot two shots due to both familiars having the same movement delay. - (Added in Repentance)
Revelation: If a revelation laser is shot through the baby, it will double the laser. - Shooting familiars: Duplicates familiar's tears.
- (Added in Afterbirth †)
Sprinkler: Tears fired by the sprinkler can be duplicated. 
Technology: When the laser passes through Multidimensional Baby, it doubles the laser.
Interactions
- (???'s Soul) ???'s Soul/
Abel/
Cain's Other Eye: Familiar tears will be duplicated if they pass through the baby. However, due to their independent movement pattern, it can be hard to achieve duplication. 
Anti-Gravity: Multidimensional Baby will travel the same path as the Anti-Gravity tears, easily doubling any stationary shots. Any moving tears that hit it will produce a normal moving copy, however stationary tears will spawn a copy that will eventually fall to the ground even after the direction is released.
- (Added in Afterbirth †) Stationary duplicated tears will release normally.
- (Added in Afterbirth †)(Baby-Bender) Baby-Bender: No effect as Multidimensional Baby only duplicates Isaac's tears.
BFFS!: The baby is larger, but tears shot through it will not do more damage.
Box of Friends: Each copy of Multidimensional Baby follows the previous copy with a 2-second ((Added in Repentance)0.66-second) delay. Tears shot through multiple babies will only be duplicated once.- (Added in Afterbirth †)
Compound Fracture: Tears that pass through Multidimensional Baby will be duplicated and cosmetically look like normal tears. Bone shards will not duplicate unless they pass through Multidimensional Baby separately. 
Dr. Fetus: No effect.
Epic Fetus: No effect.- (Added in Repentance)
Eye of the Occult: Makes it more easy to use Multidimensional Baby, as Isaac can simply stand while the familiar stays on top of him. - (Added in Afterbirth †)
Lachryphagy: Duplicates tears, which tend to merge after traveling a certain distance, making it easier to feed tears. Burst tears can only be duplicated if the tear they come from didn't pass through the baby already. 
Lil Brimstone/
Robo-Baby 2.0: Familiar lasers that pass through the baby will not be duplicated.
The Ludovico Technique: Spawns another tear that will slowly follow Isaac but cannot be controlled.
- (Added in Repentance) Spawns a stationary tear where Multidimensional Baby first appeared in the room. The tear does not follow Isaac.
- (Added in Repentance)
Mom's Bracelet: Throwing any obstacles through Multidimensional Baby will transform it into two 40 damage tears. Throwing obstacles that can drop pickups like mushrooms through Multidimensional Baby will cease the possibility of anything dropping from such tears. Crawl spaces, though, appear right after picking up an obstacle. - (Removed in Repentance)
Mom's Knife: No effect.
- (Added in Repentance)Fired knife is doubled when passing through Multidimensional Baby. No effect on held knife and returning knife.
Tech X: No effect.- (Added in Afterbirth †)
Trisagion: No effect.
Bugs
| (Bug) Bug! | Switch Can double Best Friend when it passes through. |