A large woman's white bra.
Upon activation, a picture of Mom wearing this bra will flash over the screen (similar to The Necronomicon effect). After this, Isaac is seen with the bra on his head, and all the enemies in the room will be frozen for 5 seconds.
- When Fistula (and likely Teratoma) is still frozen when it would usually split, once the effect wears off, the smaller parts will shortly be seen in the four corners of the room, then rapidly move the distance they would have taken normally, often resulting in the player taking damage. They might also get stuck in rocks. Throwing a bomb in may cause the bomb to fly around the room and potentially crash the game when it explodes.
- When using Epic Fetus, your targeting reticle will freeze while Mom's Bra is active.
- If an enemy that has an Eternal Fly circling it (i.e.: Hanger) is killed while frozen, the Eternal Fly will stay alive after the effect wears off, and will not become hostile.
- If used while Peep is in the air, he will constantly repeat his jumping animation, dealing no damage while being invincible.
- When used to kill the last stage of Satan, the two legs will turn in to the original Satan statues and the boss fight will be unfinishable. You will also be registered as continuously killing enemies.
- When using this item against Mask + Heart, the character may be stuck in a corner of the room and move to the other three while the player tries to move his character. This will wear off after a short delay of time.
- Contact Damage on the player is disabled during the active effect, so items like The Virus or damaging orbitals become more viable.