Continuity mistake: When Robin Williams puts the flubber into his back pocket to show Sara how it will bounce him back up, you can clearly see a hole in which the flubber escapes. When he falls to the ground and Robin Williams turns over the hole is gone.
Continuity mistake: When Howard supposedly has radio sex with that blonde woman, it flashes to other locations where people are listening, including one with police officers standing by early to middle 1990s Ford Crown Victorias. Howard did the stunt in the mid 1980s.
Continuity mistake: At the bachelor party, Kevin Kline has a cigar in his mouth. In one shot, it's whole, the next it's frayed, then in the NEXT, it's whole again.
Visible crew/equipment: Early in the movie, Melvin walks for the first time to the restaurant in which Carol works. As Melvin turns the corner on the sidewalk and walks towards the camera, he is surrounded by extras playing people he must dodge. If you look in the center and right background, you will see New York spectators standing in the middle of the street, watching the movie being made. (00:10:20)
Continuity mistake: After Nick becomes a hero, he wears a cast on his right arm. However, when he and Kate go to dinner with Kate's boss, Nick's cast mysteriously disappears for one shot. They are sitting at the table at the beginning of the dinner and Nick picks up a glass with his right hand, with no cast. The next time you see Nick, he has a cast on his right arm again.
Continuity mistake: When Fred Randall keeps expelling gas, the glass on his helment keeps reappearing and disappearing.
Continuity mistake: In the scene where Blank gives Debi an aeroplane ride on his feet, he takes off his cap to lie on the bed. When he gets up to leave the cap appears in his hand without his ever retrieving it from the bedpost where he hung it.
Other mistake: When Tommy Davidson and Jamie Foxx are both running and they run into, then flip over a car door that opens, if you look closely, you can clearly see the hair piece worn by Jamie Foxx flies right off his head.
Continuity mistake: In the scene where McHale rides his motorcycle out of the boat, the machine gun on the aft deck is off center (so he can drive past it). The rest of the time it's on the centerline of the boat.
Continuity mistake: When Jennifer Love Hewitt is talking to herself as she drives to pick up Will Freidle, her hair is up neatly in a butterfly clip. Then in the next shot, her hair is down. Finally, in the last shot her hair is up again.
Continuity mistake: When the two criminals are chasing Tim Robbins and Martin Lawrence on the highway, they pull up beside them and the white criminal throws his cigarette at Tim Robbins, but in the next scene he has the cigarette back in his mouth. (00:39:50)
Revealing mistake: There is one scene where Alicia Silverstone is being taken away, and in the window, in the background, you can see a metro train with the letters on the side stating BC Transit and a picture of the British Columbia flag. Yet, the whole movie supposedly takes place in Washington state.
Continuity mistake: The pile of clothes that falls onto the remote control car changes between shots. The hamper turns over as well. (00:37:35)
Factual error: Although cars are seen driving on the right-hand side of the road for most of the film, one overhead shot shows UK-style "give way" lines across the left-hand side of the road.
Character mistake: In the Liverpool match the commentator says that Liverpool could win their 19th title, in the 1988-89 season Liverpool had 17 titles, and won their 18th title the year after in the 1989-90 season.
Visible crew/equipment: In the scene where Lars is in the string factory alone and the machinery pulls on loose threads on his clothing, there is a shot where a crewman's arm can be seen through some mesh holding the thread.
Visible crew/equipment: In the scene where Lily and Dan are doing it in the car, you can see someone sitting in the front seat in the car rocking it.
Continuity mistake: When David tells Kevin and Jennifer about Bean staying at their house and he says "Let's say there is a chart of the most intelligent people...", you can see a blue pillow on the couch which Kevin and Jennifer are sitting on. When it cuts to a shot behind them you can see the pillow is on Kevin's lap. When it cuts again the pillow's back on the couch. (00:08:15)
Audio problem: As they are running away in the ice cream truck, Ed turns on the jingle and starts dancing. Dexter gets annoyed and turns the jingle off, but the music stops about a second before he hits the button.
Continuity mistake: When the kids are telling Beaver that he has to climb into the teacup, the kid with the heabands hair keeps changing. In one shot, it's hanging over the headband, and in the next the headband is in front over the hair, and it keeps going back and forth.