Revealing mistake: During the bedroom scene with Felicity and Fat Bastard you can clearly see the air hose that fills his suit when he rolls over in the bed.
Continuity mistake: In the scene when Mini Me and Young Number 2 grab for the cookies, when Young Number 2 grabs there are two, one that looks like chocolate chip, and a plain one. When Mini Me grabs for it there is just one.
Continuity mistake: When Mini Me and Austin are fighting on the moon Mini Me bites Austin's spacesuit and you can see his British flag underwear. But after he sends Mini Me out into space, he drops the space suit and Austin is now wearing a blue jumper with no holes in it.