Summons a ghost near Isaac that will follow him around, and summons a controllable blue crosshair. After a few seconds, the crosshair disappears, and the ghost will act depending on what the crosshair was targeting:
Enemies: Attacks the enemy until it dies or can no longer be targeted due to a form change or similar cause. The ghost does 3 damage per tick, for 9 damage per second. BFFS! does not increase this damage.
Doors: Opens the door, even if it is locked. Functions the same as Dad's Key when being used in this way. This includes the door to Mega Satan, exiting Hush's room, and exiting Boss Rush.
This does not work on A Strange Door. However, it does work on doors leading to alternate path levels.
Unlike chests, stealing an item pedestal from a Challenge Room will trigger the waves to spawn upon picking up the stolen item.
In rooms with multiple pedestal items where only one can be taken, if the ghost is carrying a pedestal while Isaac picks up a different pedestal item, the ghost will disappear. This prevents taking both items for free.
Using Mr. ME! with Tainted Forgotten does not work as displayed. Mr. ME! will not follow the crosshair, instead it will target where the Forgotten is thrown.
Book of Virtues: Spawns a wisp that looks like a face in the middle ring. The wisp cannot shoot. If the current room is cleared, the wisps automatically move toward and unlock chests and special room doors, destroying themselves in the process. The wisps can open ANY locked doors, including the ones to Mega Satan, the Ascent, and Corpse. Stone/Mega Chests are unaffected.
Car Battery: May sometimes glitch pedestal items, resulting in Isaac being unable to pick them up without leaving and re-entering the room. Otherwise has no effect.
Sack Head: If Mr. ME! successfully stole a consumable from the shop, there is a chance he will drop a sack instead.
If the Devil Room or Angel Room disappears after leaving it, using Mr. ME! will still attempt to unlock the doorway back to it. This allows you to move through the wall as if there were a door there, but you will not be able to enter the Devil Room or Angel Room.
If used while shooting with Marked, the crosshair will continue straight in the first direction Isaac shot at, and cannot be controlled until Marked is deactivated.
Mr. Me is able to damage Mom's doors even when no body part is sticking out of them, Mom's Heart and It Lives while they're withdrawn, and Isaac and Hornfel while they're off screen. He never loses them as a valid target, eventually killing the boss.
Attempting to use Mr. ME! to open alt. chapter doors will sometimes crash the game.
Attempting to use Mr. ME! to buy a devil deal item in the boss room (after the use of the Satanic Bible) crashes the game.
Using Mr. ME! right before the Tainted Lazarus transformation will lead to the ghost standing in place until the room is left.