Other mistake: 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.
Continuity mistake: 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.
Visible crew/equipment: A short scene opens with an alternate couple in an opposing hotel suite to the one the bachelor party is in full swing at. The guy relaxes the woman by telling her he is just going to open the window for some fresh air, and as he walks to that window and is about to open it, the boom mike can be seen. This appears on the Australian VHS release of this movie. (01:16:30)
Continuity mistake: In the fight scene at the end with Rick & Cole in the theater, the couple in the front row are slouched down in their seats throughout the fight. Right before the woman gets hit in the face, the couple are sitting up and the guy has his arm around the woman.
Revealing mistake: When the Hotel manager walks in the recently vacated room, we see the piano collapse. If you look closely, you can tell that the front two legs were just pulled back under the piano causing it to collapse.
Continuity mistake: When Cole and Debbie get into the pickup truck near the end of the movie, the man sitting on the back of the truck is wearing an orange hat with a white front. When they reach the theaters and the truck comes to a stop, he is now wearing a white hat with an orange front.
Visible crew/equipment: As the donkey is eating pills off the table, you can see the fingertips of the crew person, manipulating the animal's tongue and jaw as it 'snorts' the lines of white powder coke, indicating it is a puppet.
Other mistake: As Rick and the gang rush around the cinema looking for Cole and Debbie the cameras jostle a bit up and down then steady again.
Continuity mistake: At the end of the movie when they are are all running out of the hotel, Rudy is running with the dancer and his shirt is open the entire time. When he gets to the end of the alley his shirt is neatly buttoned and tucked in.
Audio problem: At the party when the dancer is approaching Rudy some of his screams don't match up to his mouth.
Continuity mistake: When the hotel manager watches the piano collapse, you can see through the window that it is dark outside. The scene then cuts to the hotel lobby where you can see daylight through a side window, then the front doors.
Chosen answer: It's showing he's sexually adventurous, as he's using a cooking appliance as a sex toy.