Continuity mistake: When the red Sunbird and the Caddy are driving sown the steep hill, the windshield on the Sunbird changes from passenger side busted out, to completely gone, to completely intact, when they hit the tree at the bottom. (01:18:15)
Revealing mistake: There's one scene where they are surrounded by the foot. Leonardo reaches behind him for his katanas, but he doesn't unsheath them. If you look at his elbows, you can see gaps in the pads where the actor in the suit hasn't fully fastened the gloves to the rest of the outfit. (01:05:40)
Revealing mistake: Junior can't get on the Crazy Dance because he is a milimeter too short. After seeing Murph (the 20-year old in his class) and Trixie (on heels) get on it, Junior speeds up the ride and all the kids on it get dizzy and barf everywhere. If you look where the puke shoots out, it's a bit obvious it's not coming from their mouths, but from a point behind them. Most obvious are Trixie and the boy wearing glasses.
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)
Revealing mistake: When Alice trips and falls on the staircase, the Woman gets on top of her and tries to stab her. Throughout their struggle, you can clearly see that Alice is in fact replaced by a stuntman. (01:28:00)
Revealing mistake: When Charlie shoots the critter which flies into the air and explodes, we can see the wire the critter is attached to. (01:07:45)
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)
Revealing mistake: Near the start of the film, when Lt. Harley is watching his love interest show off by doing gymnastics on the tree limbs, several times you can see the actual pole she is swinging on, not the tree limb. (00:08:50)
Visible crew/equipment: In the scene where Jack approaches Parry's bed, a crew member is seen on the right hand side of the shot wearing a walkie talkie. He inches out of frame in 3 or four seconds. (01:51:05)
Continuity mistake: Towards the end of the movie, when the mob appraiser has verified the medallions are authentic, he is wearing two white gloves. He then asks if he can leave. When he stands up and gathers his things, he has only one glove on. The shot cuts away. When it cuts back to him, he has two gloves on again. (01:32:50)
Continuity mistake: When Steve Martin is going berserk in the grocery store he is wearing white socks as he runs away from the assistant manager. In the next scene in the jail cell, he's wearing black socks.
Continuity mistake: At the start of the quicksand scene, Campanella is carrying his jacket over his shoulder in the initial shot but not in the next one. (01:01:21)
Character mistake: Whoever wrote the "homicide" memo on the captain's corkboard spelled "homicide" wrong.