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.
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.
Continuity mistake: When Austin and Foxxy are confusing Mr. Roboto's words, the plate of food on the table changes between shots. Sometimes it is in front of Austin (even after Foxxy moves it), sometimes it is in front of Foxxy, and sometimes it is missing altogether.