Deliberate mistake: When the saloon patrons pour through the swinging doors in pursuit of Packer, the same people are seen repeatedly. A relatively small number of extras are running around to the rear of the set and re-entering through the back so that they will appear to be a larger crowd of people.
Deliberate mistake: When the brother enters the basement for the first time, the Canadian team is not dealing Canadian dollars, but Australian dollars.
Deliberate mistake: When Buddy's dog box falls out of the back of the truck the dog box is empty.
Deliberate mistake: Every time George swings into a tree, there is a George shaped impression created. However, in the next scene the tree is back to its natural shape.
Deliberate mistake: As the Mondo Burger building is falling apart, customers and employees run out the doors. The glass doors then shatter. Not only do they break at the exact same time, there was nothing to make the windows shatter as hard as they did. (01:25:51)
Deliberate mistake: In the finale when Kadeem Hardison is beat up by the motorcyclists he performs a back somersault. As he falls to the floor, you see a white guy's back, despite the character being black.
Deliberate mistake: The same shot of the railway station concourse is used when Graham and George are heading to work, and also when George commits suicide. The giveaway is that several people are seen in the same position. (00:05:00 - 01:20:30)
Deliberate mistake: The man kissing Cameron Diaz in that last shot (when the homeless guy shoots the drummer) is not Ben Stiller, noticeable by his much taller, slender figure. (01:52:40)
Deliberate mistake: The floating contact mine that explodes at the end of the movie would never have been put in an evidence room in a police station. Barring that error for the plot's sake, FCMs weigh 450lbs and would have required a hydraulic crane and a cart to move it, not just a couple of guys. They also did not contain clocks. (00:42:40)
Deliberate mistake: When Mark is catching a cab outside "JFK" airport, the cars are driving on the left hand side of the road - if they were in America they would be going the wrong way (the director points out in the commentary that this shot was filmed in London to save money).
Deliberate mistake: The shot of Orbison's house buring at the end is quite obviously fake. You can see that it's made of cardboard and paper, and even the windows burn and curl like normal bits of paper do when set alight.
Deliberate mistake: Towards the end of the film, Josh is playing a game in the park with Vinnie, and Vinnie asks "What's that?", to which Josh replies "Schliemann Attack." However, this dialogue occurs while the game is still in standard opening theory and before Josh has played the move that introduces the Schliemann Attack (pawn to f5).
Deliberate mistake: When the fight first begins on deck of the sub, a henchman jumps from the hatch and picks up a wrench that was lying on deck. If the sub just surfaced, where did that wrench come from?
Deliberate mistake: In the beginning of the movie when Happy first discovers his swing, the balls that hit the people down the street are never visible upon impact.
Deliberate mistake: When Jen Moo and Ching fling back the fire bombs thrown by Leong Kit, they set the rear ends of his students on fire. But since they were all standing facing front and dispersed around the altar, they would be most unlikely to be hit that accurately in that particular place.
Deliberate mistake: Throughout the movie, you can see the size of true-size Rosemary, particularly her waist and legs. Notice the size of undies she was going to purchase when she and Hal first meet. Notice the size of her bathing suit bottom. However, in the scene where she throws her purple nightie undies at Hal and he catches them: the panties are WAY TOO BIG. Especially the leg holes, which could go around her true-size waist.
Deliberate mistake: In Monsters, Inc., when Mike and Sulley walked through Monstropolis to go to the company, Mike said to Sulley "You've been jealous of my good looks since the fourth grade". In this film, we're told Mike and Sulley met in college. [In the commentary, director Dan Scanlon explained that there was a lengthy scene that would have followed Mike and Sully throughout their years in elementary school, but it would have slowed the pace of the film and would have reduced the impact of their rivalry. Rather than spend a lot of time on a back story, Scanlon decided to have Mike and Sully meet in college, even though this was inaccurate.]
Deliberate mistake: The floating candy bar that clears everyone from the swimming pool is a Baby Ruth, but Baby Ruths don't float, they sink like a rock.
Deliberate mistake: The film uses Milwaukee County stadium,instead of Cleveland Stadium, as the home of the Indians. (00:26:10)
Deliberate mistake: The 45's advertised as new releases on the record store sign actually came out at different times throughout 1955. A true selection of new releases from early November 1955 would have most likely included minor hit singles that 80's moviegoers wouldn't have recognized. The songs listed were some of the biggest hits of that year and were obviously chosen for their ability to help set the musical tone of the time. (00:34:30)