Continuity mistake: At the beginning of the movie, Harry's van has bucket seats, yet later on when the "gas-man" rides along, he is sitting on a bench seat in-between Harry and Lloyd.
Continuity mistake: When Lloyd tackles Mary on the hotel stairs, she is wearing black pantyhose. By the time they get to the hotel room, she has miraculously changed into grey tights.
Visible crew/equipment: When Lloyd is daydreaming about Mary as the doors to Mary's house open and Lloyd picks up Mary. He lifts up her skirt to show a little flesh, in the background you can see the feet of two crew members laying on the ground holding the doors open.
Continuity mistake: When Lloyd drops Mary off at the airport and hugs her goodbye, in the background there are two men walking towards them. The camera changes to the angle behind Mary then behind Lloyd and then back to the side. When it returns to the side view the two men are farther away but still walking toward them.
Continuity mistake: When Lloyd asks if the bartender knows Mary, he originally grabs the bartender with the left hand. But in the next shot he lets go of him with his right hand.
Audio problem: When Harry and Lloyd pick up the hitchhiking natives, when they were playing the mockingbird song, the guitar was playing but his hands weren't moving at all.
Continuity mistake: When Harry and Mary go out on the date to the ski resort, when they get into a snowball fight, the camera shows Harry, and it's snowing, but when they show Mary (who is supposed to be right beside him) it is not snowing. It keeps doing that, when it shows Harry it's snowing, and Mary it is not (or vice versa).
Continuity mistake: After leaving the diner, Lloyd & Harry are pulled over by a motorcyle cop (Harland Williams). As the cop notices the beer bottles on the floor of the van, you'll notice his hair has a curl hanging over his forehead. Right before he takes a drink of one of the bottles, the curl is gone. It cuts to Lloyd & Harry trying for a brief second , and when it cuts back to the cop saying "You'd shut your mouth if you knew what was good for ya," the curl is back.
Visible crew/equipment: When Harry and Lloyd are leaving Providence, there is a hand moving the curtain behind Harry.
Continuity mistake: At the truck stop, in the side shot in which Lloyd tells Harry to toss some salt over his right shoulder, Harry is holding his straws at an angle off the table. Then it switches to a front shot of Harry, and he is now holding his straws vertically on the table.
Continuity mistake: When the "gas man" falls to the floor due to the atomic peppers that Harry and Lloyd sneaked into his burger, Harry and Lloyd laugh at him, and Lloyd even points at him. Then he stops pointing at him and looks at Harry. But only a moment later, in the very beginning of the next shot (a close-up of Harry and Lloyd), Lloyd is instantly pointing again.
Continuity mistake: When Lloyd states that the map says they've only drove a quarter of an inch, you will see a creek with a unusual tree growing around it. You see the same creek and tree when Harry and Lloyd pick up the "gas man".
Visible crew/equipment: On the DVD when Harry is in the bathroom (from the ex-lax) as he sits on the toilet if you look on the floor you can clearly see the dolly track for the camera.
Other mistake: In the brief scene in which Nicholas Andre and J.P. Shay are talking about the killing of the owl at the preservation society ball, if you look very closely out the very bottom of the window, at the very end of the short scene (right after Andre says, "Their guys aren't just anybody, they're good"), you can catch a brief glimpse of part of the box containing the victim who is trying to escape (this box was completely excluded from the film).
Continuity mistake: After Harry and Lloyd start gagging over the atomic peppers, we see a brief shot in which everyone else in the restaurant looks at them (and the waitress suddenly appears in that shot as well). But in very the next shot (back to Harry and Lloyd, still gagging), nobody is looking at them (and the waitress, who was there just a moment ago, disappears).
Continuity mistake: When Harry and Lloyd start singing "Mockingbird," we see a front shot of the "gas man" getting annoyed and gritting his teeth. Then it switches to a side shot, and his annoyed expression is now different, instantly.
Continuity mistake: When Jim Carrey and Jeff Daniels are in the restaurant, just before they encounter Seabass and right after they call the waitress "Flo", Jeff's coke glass is on his right side. The next shot shows it on his left, then his right, then his left again, without him touching it.
Revealing mistake: The Aspen lift operators are wearing Copper Mountain uniforms. Copper Mountain is in Colorado, but it is over two hours away from Aspen.
Revealing mistake: When Harry and Lloyd are at the restaurant with the kidnapper they give him the hot peppers. Then he falls to the floor and Lloyd is trying to give him C.P.R. If you look in the background you can see the waitress laughing in the first few shots.