Deliberate mistake: The car Rudy, the mechanic, is working on is a 1971-72 Plymouth (the one where the chassis falls down around him). Plymouth's of that era were unibodies, which means that the body and the chassis were all one piece and not separate, so there's no way a chassis could have fallen down like that from that particular car, since it didn't have a separate chassis.
Deliberate mistake: When Prince Hapi says that Monique should be his seventh wife, she says "you have seven wives?" and he confirms. Actually if she is supposed to be his seventh wife he only has got six wives by now.
Deliberate mistake: In the opening credits, there is a newspaper article showing that Dirk Pitt has found the remains of Nungesser and Coli's L'Oiseau Blanc, a plane that disappeared attempting to cross the Atlantic in 1927 before Charles Lindbergh made it. The wreckage in the newspaper photo is totally wrong; it has a radial (round) engine and cowling and a three-bladed propeller. The real plane had an inline engine, square cowling and a two-bladed propeller.
Deliberate mistake: When Boyd has saved the Vice President's life after chucking him into the water, Boyd looks down at the VP who is being dragged out. Suddenly, there is a picture taken that appears in papers, but there was no press or person on the bridge where Boyd is with a camera, so where did the photograph come from? (00:06:55)
Deliberate mistake: When Tiff (as a doll) lights her Zippo you don't see her clicking the flint, even though one can hear a 'clicking' sound. (00:33:35)
Deliberate mistake: The balloon llama the chipmunk makes has legs which are completely detached. The pairs of legs should be twisted together. Without this, it looks like the balloon has 6 different ends.
Deliberate mistake: When Kate Barlow shoots the Sheriff, she shoots him between the eyes, but when she kisses him there is no hole or anything on his face.
Deliberate mistake: This has the old T.V. show style "it was 6 a.m. on January 7th we ... " beginnings to the scenes. Pay attention to those times and dates. They're not even close to being in sequence. I mean days, not just times.
Deliberate mistake: When Tom Hanks is picked up at the airport by a taxi, its license plate number is TX7943. Later when he is picked up at the Ramada Inn, he is picked up by a taxi with a different driver, different numbers on the top, but has the same license plate number.
Deliberate mistake: With John Cusack leaning to the side to pull Diane Lane and the dog from the water, the rowing scull should have nearly tipped over, yet it leans only slightly. Later in the same scene, the normal instability of such boats can be seen when tipping occurs to a greater degree simply from the dog moving.
Deliberate mistake: Whenever we see the computer generated Lou, he never has genitals.
Deliberate mistake: Old Weird Harold's pants fall down twice in the film. His boxers are different colors each time; once they're red, the other time they're blue. The director admits to this deliberate mistake in the commentary, siting his interest in seeing if people will notice.
Deliberate mistake: When Layla is having babies and the first one comes out there is already a nappy on the baby. (00:06:45)
Deliberate mistake: In a couple of scenes, Bandit's Trans Am's engine sounds are dubbed, and you can hear the shifting of a manual transmission when his car was an automatic.
Deliberate mistake: When Chosen One is dancing in front of Betty, take a look at Betty's face. There is a moment in which the face of the double playing Betty is visible.
Deliberate mistake: In the championship game, when number three on the other team hits a home run, he never touches home plate. Home plate is where all of the players are crowded around (primarily the ones to the left of the scene). The player makes a "jump stop" at the batter's box. The Bears could have waited 'til the player went back to the dugout; the catcher, with the new ball in play, would have stepped on home plate, and the home run never would have counted.
Deliberate mistake: At the end when Ali smokes the huge spliff, look in the difference in length between when he first lights it and starts smoking it and when he starts blowing the smoke out. It's about 10 times smaller in the second shot.
Deliberate mistake: When the neighbourhood kids are teaching Dickie to ride a bike, whenever he hits something his brown hair dye, that he applied a few scenes back, is missing from his hair (obviously a stunt double is in place for David Spade).
Deliberate mistake: After the first scene where Hannah's ex-husband walks in without knocking and picks up the kids, Hannah is looking at some family pictures including her, her ex-husband, and the kids (supposedly taken when they were still married). But in the pictures they're all wearing the exact same clothes that they were in the previous scene. Could be a coincidence but that seems doubtful.
Deliberate mistake: At the beginning, the carolers are on the porch singing. The camera never pans, so this means that the carolers are facing away from the house (towards Gate) - seems rather odd. The only reasons for this would have been to make the clean camera move through the crowd and up the house.