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)
Continuity mistake: When Maurice is tossed out of the tavern we get a nice view of the front with its large hanging sign, but after Gaston whispers his plan to LeFou once again we see the front, which is quite different. The sign is gone, and now there are horns hanging on the awning, etc.
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: After finding his son hit a home run in the game with the pirates, Peter decides he must learn how to fly. The ball his son hit comes flying from the sky and hits Peter in the head, knocking him over. When he hits the ground, he is lying on grass, but one second later he opens his eyes on grey rock. (01:28:10)