Continuity mistake: When Harry sits down on the toilet and lifts up his legs, his eyes are closed, and they remain closed until the very end of that particular shot. Then, when it switches to the front shot of Harry a few second later, his eyes are open, right from the very beginning of that shot. And if you look closely at that shot change, you don't see Harry do the action of opening his eyes - they just change instantly between the shots.
Visible crew/equipment: When Harry gets pulled over the officer's sunglasses reflect the camera man.
Suggested correction: You must have really rich imagination to see cameraman in those glasses, after really hard examination I don't see nothing but the sheepdog minivan there.
Factual error: When the airbag blows in Lloyd's limousine, it stays inflated - it should instantly deflate. (00:08:40)
Other mistake: At the start of the film when Lloyd pulls up next to the Austrian woman, despite being tinted we can see through the limo's window. We don't see Lloyd climbing from the front to the back of the car, nor do we see the car rocking slightly which it would have done if someone was moving around inside. It's also impossible for him to get from the front to the back of the car in the time given.
Continuity mistake: During the diner sequence, the amount of fries in Harry's basket changes between shots.
Continuity mistake: In the scene when Harry stops and says to Lloyd,"look at the butt on that", there is a man with a blue coat that walks behind them into a store. When Harry and Lloyd turn around to keep walking, you can see the blue coat man entering the store once again. You may have to freeze frame it to see the man the second time. (00:57:45)
Continuity mistake: When Harry has his tongue stuck to the chairlift, there is frost on the pole when he licks it. Later, when he asks the kids for a cup of warm water, there is none. Then when Mary removes his tongue, the frost is back. (01:14:35)
Revealing mistake: When Lloyd drives into the back of a car at the airport his air bag inflates and it looks it is made out of thin rubber translucent material. That is not what real air bags are made of. (00:08:40)
Continuity mistake: When the policeman is driving next to Harry and Lloyd's van telling them to pull over after their encounter with Sea Bass, the lines on the road are single broken lines. After they pull over, the police man walks over to the van and the road lines are double solid. (00:27:45)
Continuity mistake: Speaking of the airbag mistake, how about the fact that the hub of the steering wheel in the Cadillac Limo was small, and could no way have an air bag behind it? (00:08:40)
Continuity mistake: In the Unrated Version DVD, in the van sequence after Lloyd's second encounter with Seabass in the restroom, Harry says that he will stop talking about Lloyd's encounter with Seabass. Lloyd turns his head and looks over at Harry. Then it switches to a close-up on Lloyd from the other side, and we see him repeat the same action of turning his head and looking at Harry, this time more sharply.
Continuity mistake: Lloyd reads the article about Mary and can't even pronounce the word "the", yet when Harry says look on the briefcase for her name, he says "Samsonite" with no problems, and Lloyd can easily read the "Man Walks On The Moon" newspaper headline in the hotel bar.
Suggested correction: That isn't a continuity mistake - it is meant to be funny or ironic... or part of the "dumbness." Humor is often comprised of violations of expectations. He can read a big word like "Samsonite" but not a three-letter word like "the." (Less likely, it is also plausible that he didn't actually read the word "Samsonite" but recognized it as a name-brand symbol).
Continuity mistake: In the scene where Lloyd is making drinks for him and Harry, there is a half full bottle with something that looks like whisky in it. Then the cameras changes angle to Harry for 2 seconds, and then again back to Lloyd, but suddenly there isn't half as much "whisky" in the bottle as before. It is impossible that Lloyd could have poured so much "whisky" into the glasses in only 2 seconds. (01:19:40)
Continuity mistake: When Lloyd and Harry are in the restaurant notice Lloyd's fork. In the side shot there is no fork, but when it changes to a front shot the fork appears. This happens several times throughout the scene. (00:22:00)
Continuity mistake: At the ball Helen and Harry are talking and in the background you can see Lloyd and his hat is on the bar. A second later he shows off his butt and he is holding his hat. (01:10:29)
Continuity mistake: There is a scene just after Lloyd meets Beth in the bar when Mary is skiing along and looks around for Harry who is still stuck on the ski lift. The shot is comprised of a long shot of her skiing to a grey marker and then a close up of her stopping and looking around. It is obvious in the shot when she comes up to the marker that the woman on the skis has much darker hair than Mary and is her "ski double". (01:13:20)
Continuity mistake: When Mary leaves her briefcase on the airport floor, Jim Carrey is seen running and sliding to the briefcase. In the scene directly preceding that, he is nowhere to be seen, yet instantly he is teleported within 20 feet of the briefcase. (00:09:35)
Continuity mistake: When they have left the cafe without paying, and Lloyd has to pee, Harry's hair is blowing in one shot because the window is down and in the next shot the window is up and his hair is not blowing. This goes back and forth for the duration of the scene. (00:26:00)
Continuity mistake: When Harry and Mary go out on the date to the ski resort, they get into a snowball fight. When Harry is shoving her face in the snow, the first time it shows Mary she is facing one way, but when they show her again she is facing a different way. In addition to this before the camera cuts to a different angle on Harry you can see Mary's nose is bleeding immediately after she stands up. The camera then cuts to a different angle and it isn't. (01:18:21)
Plot hole: By the time Lloyd gets to the airbridge the plane had already left. The finalisation of the boarding process after last call, plus push back takes at least 15 minutes. Lloyd would have easily caught up to Mary or the plane would have still been there.