Continuity mistake: At the beginning, there is a scene where Ben spills a carton of milk. He picks it up right away, but a split second later the scene changes, the milk is still lying down, and he puts it upright again. (00:06:25)
Revealing mistake: When George Newton comes into the house and it is raining he has an umbrella in his hand. If you look outside his door underneath the balcony it's wet, but further down the path the ground is dry.
Continuity mistake: When Lionel's mum gets bitten at the zoo, the colour of her sleeve material changes from black/dark blue to light blue. (00:17:45)
Visible crew/equipment: In the scene where Scott and Fran are dancing on the roof and the camera is about to pan downwards towards the lower level, to the left of the clothes-line, someone's head is visible moving. It is a crew member sitting against the other side of the wall.
Continuity mistake: Betty Lou is in the grocery store at the checkout. The cashier rings through her groceries which consists of a roast, veggies, flowers, dog food and a bunch of other things (she was shopping for her anniversary dinner), but she only leaves the store with the flowers.
Factual error: Throughout the film, the drainpipes on the buildings are almost all plastic - the film is set in the Victorian era.
Continuity mistake: During one scene, Mel Gibson is talking to the young boy through the treehouse door and holding the boy's jacket. The next scene, there is no jacket and then it magically reappears. (00:35:30)
Continuity mistake: In some shots there is no steam coming from the steamboat.
Continuity mistake: In the outdoor restaurant scene (where Tim Robbins has just spoken to Burt Reynolds), the waiter brings Tim Robbins a bottle of water and a wine goblet, but when he pours the entire bottle of water into the goblet, it's obvious that it was not a full bottle of water to begin with. It doesn't fill the glass of half way. A waiter would not serve an opened bottle of water to a diner.
Revealing mistake: In the chase scene about an hour into the movie, Robert Loggia is shown entering the Liberty Tunnel, driving on a wet road. Note the vaulted round ceiling of the tunnel. Next, we see a series of shots of him in the tunnel, and then a shot of the sun rising over Pittsburgh as he is about to leave the tunnel. Here is the problem - the sunrise shot is taken from the Fort Pitt tunnel on a different day. Note the dry road, the barriers to the driver's left at the tunnel exit and the Fort Pitt bridge straight ahead. There is no place for the driver to make a left turn out of this tunnel. Also note that the POV is from the left lane. All the Liberty Tunnel shots show Loggia in the right lane. The next shot shows Loggia exiting the Liberty Tunnel and making a left turn from the right lane, causing a pile-up. (01:11:10 - 01:12:20)
Plot hole: At the end of the movie, when Lonette comes across Frank's dead body, she asks Nails what happened. Nails tells Lonette that he was pushed off a building by Holly Wood. Lonette then asks if Holly was in doodle form when she killed Frank. Nail says she was. There would be no way for Nails to know either of these things as he was trapped in the fountain pen when Frank died and wasn't released until the Spike Of Power was removed.
Continuity mistake: When Chester is trying to get Matthew to come into his car after school, Matthew has a football in his hand for a couple of shots. Then, the football disappears and his replaced by his backpack for the last shots of the scene.
Continuity mistake: When Eddie Murphy is on a duck hunting trip with a bunch of gun lobbyists, the lobbyists are firing their M16 rifles at a bunch of ducks that are flying by. You can clearly see them squeezing the trigger and not a single shell case is coming from the chamber of the gun. Also, when you fire a gun there is usually smoke from the muzzle but in the movie there is no smoke, yet you hear the sound of several guns firing. (00:55:00)
Visible crew/equipment: When Ethan is going into the space ship, one of the critters pursues him. We then can see a man's shadow on the ground, most likely the cameraman's shadow. (01:04:15)
Other mistake: When Tod is going outside to see a statue of himself, as he gets closer to the door he runs into it, but he actually jumps at the door.
Revealing mistake: When Nick returns to his apartment (after being made invisible) he immediately closes the curtains. Although he is invisible, we should see the curtains pulled closed at the point that he grabs them with his hands. Instead we see them close from the top, revealing they were closed either by a crewman or an automated process. Note: The curtains are NOT meant to be automatic in the film as we see and hear him physically close them.
Other mistake: When the girl throws a grenade at the closed window it rolls a bit and you see that the bottom has been drilled out.
Continuity mistake: In the scene when Hasari comes back from work and he has got the school girl as a permanent customer, his friend goes to Kamla and tells her that Hasari has had a good day, and she closes the pot. Then a side shot of Kamla and Hasari is shown and you see her close the pot again..
Factual error: The old man is supposed to have accidentally ended up at Rita and Peter's wedding by just "getting on a train," and finding himself in Lake Forest (a far northern suburb of Chicago.) But he started out in Berwyn (a western suburb), and in order to get to Lake Forest from Berwyn, you have to get on one train, get off in downtown Chicago, walk several blocks, and then get on an entirely different line going to Lake Forest. In other words, not something you can "accidentally" find yourself doing, but something you have to know where you are going in order to do.
Continuity mistake: When Jacques attaches the bungee cord from the cocktail cart to Lazlo's pants, Lazlo takes a step forward and the cocktail cart snaps after him causing a terrible ruckus, however the bottles on the cart mysteriously empty before the collision, and none of them move. They are obviously glued to the cart.