Revealing mistake: In the beginning right before the opening dance number begins, Gwyneth Paltrow and Steven Spielberg (in cameo roles) do back flips. You can see the stunt double doing them as the stunt double was wearing a blond wig (depicting Paltrow) that falls off after the first flip. (00:04:22)
Revealing mistake: In the scene when Austin Powers goes to visit Dr. Evil in prison to ask about his father there is a shot of Dr. Evil with Austin's head partially in it. If you look at his reflection in the glass, you see he looks nothing like Austin. The person in the reflection is actually a body double. (00:21:20)
Revealing mistake: When the first sumo takes off his "diaper" and throws it in the basket, you can see he is still wearing something.