Continuity mistake: After leaving the Bookseller store, in an overhead shot Belle passes a shop just as a woman is pouring water towards the downspout, and in the next shot the shop suddenly has a large hanging pipe sign with a table under the window, the green shutters have vanished on the right window, the half-timber wall pattern and wood trim have changed, etc.
Continuity mistake: After making the mud-pie Fred jumps into his box. In the closeup as he lands in it and Elizabeth closes it, you can see Elizabeth has pink trainers on. In the previous and following shots she has white socks on. (01:02:50)
Other mistake: When Gomez begins to flip through his desk calendar, we see that "today" is Thursday, March 28, 1991. He then turns to the date of the "next quarter". The left hand page shows Thursday, August 8, but the right hand page shows Tuesday, September 9. (00:11:15)
Revealing mistake: When Bill and Ted leave the house with their "bad" selves, Keanu Reeves' double is seen as they move past the camera. (00:21:20)
Continuity mistake: When Pockets is shooting paint at the pirates, he sprays yellow paint on a pirate's face on the right, who crouches and touches his face blinded. Shot changes and not only is the painting gone, but the pirate is calmly sword fighting with a kid. (01:53:38)