Continuity: In one scene, Tom Hanks leaves a room while the last part of "Something Isn't Right" by Oingo Boingo is playing. When he reenters the room, the middle of the song is playing.
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In one scene, Tom Hanks leaves a room while the last part of "Something Isn't Right" by Oingo Boingo is playing. When he reenters the room, the middle of the song is playing. See more...
Bachelor Party mistakes
Other: In the beginning of the movie, when the mechanic is working on the car on the lift, he says he has to change the oil in it, the chassis drops to the ground, there is no engine attached to the chassis or body. In addition, he is changing the oil at the rear axle.
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.