Factual error: When Scarlet decides to ram the other car, she asks 'Him' if there is a green Pontiac behind her. Him answers yes. In fact, the car is a Chevrolet Camaro, not a Pontiac. Him may be a detached actor that knows nothing about cars, but Scarlet knows the car and its owner well, and the owner's reaction proves the car hit was the intended target. (00:29:15)
Audio problem: At the end when the guys are singing the musical number, Steve-O is coming up from the water saying "Now" but he is saying it backwards making it obvious the scene was reversed.
Continuity mistake: At the beginning, when Benny G is sitting in his car listening to the remake of his song "I Cry" on the radio, in the exterior shot of the car there is a massive amount of water on the window. But, in the interior shot, there is not as much water on the window anymore, and there was no time between shots to put the windscreen wipers on.
Plot hole: When Farley is preparing to rescue Simon by towing him up with the rope attached to his van, he drops his "cigarette" into his crotch, causing him to floor the gas pedal. His back wheels begin to spin. This is impossible because the vehicle is still in Park. There is even a camera shot of the "PRNDL" proving this. I guess this goof is employed by the filmmaker to increase the dramatic effect of him subsequently slamming the Dodge into drive a second later and careening through the fence. (01:07:35)
Factual error: Jenna calls her dad with the result of her sonogram, and reveals the sex of the fetus. But given the timing of the movie, we know that Jenna is between 10 and 12 weeks - gender can't be determined from a sonogram until at least 20 weeks.
Continuity mistake: When Yankee goes into his bedroom after losing the baseball game in the sandlot, he tears a hand-drawn picture of himself, Babe Ruth and his dad off the wall. The pieces of the picture fall on the bedroom floor. A few shots later the pieces are missing. Yankee was the only one in the room, and he didn't move them. Plus the window is closed, so it couldn't have been wind.
Continuity mistake: When Roger is drunk and getting into bed, his alarm clock changes from 11:39 back to 11:38.
Continuity mistake: When the monster puts down Hanso after she tries to escape, you can see her footwear is completely dirty, but in the next shot where the monster's tail uncoils itself from her body, you can now see the pink and white of her footwear that you couldn't see before.
Continuity mistake: At the garden party, when Scarlett Johansson is sitting on the bench and talking, her hair is alternately tucked in and then on the outside of the sideframe of her glasses.
Continuity mistake: In the scene where Marilyn arrives at the bar to see her friend Liz, as she sits down there is only a bowl of olives in front of her. A few shots later, there is now a drink in front of her as well. Never during the scene does she order a drink, or does a bartender set one down in front of her. (00:33:15 - 00:34:25)
Continuity mistake: In the second wedding scene the amounts of confetti everywhere, changes.
Plot hole: When Melvin receives the phone call from a lost Diana, he is staring at his goldfish, swimming peacefully in the bowl in his apartment. He unsuccessfully attempts to rescue Diana, then goes to the night club where he encounters an inebriated Ginger. He escorts her home, rebuffs her advances, and goes to his own apartment. The next morning, he goes to her job site, where, inexplicably, the goldfish has now taken up residence. Unless Ginger's flunky somehow broke into Mel's apartment and absconded with the fish, there is no way the fish could have gotten there on its own.
Factual error: To demonstrate his hatred of the England football team, Paul throws darts at a photograph of the players in their red shirts midway through the competition. However, the photo in question was taken after the final was played. Furthermore, in relation to the film's timescale, when the scene takes place neither the team or the choice of kit had been decided upon.
Continuity mistake: In the scene after the 'one year later' title, where Anderson wakes up on the couch, he is wearing red plaid boxers. The following shot shows him feeding the mouse, followed by a shot of Anderson again, but this time he is wearing grey underwear while he drinks pickle juice.
Continuity mistake: Right after Karen bites her father's neck, a bandage is placed on it. Immediately after this, Gerald fights his way to the house and they let him in. For several shots, there is no bandage, wound, or even blood on the father's neck while Gerald is explaining what's been going on. Then suddenly a close-up of the father shows that the bandage has re-appeared without anyone putting it there.
Continuity mistake: When John C. Reilly is in the dressing room telling the airplane story, the time changes back and forth on the clock behind him.
Continuity mistake: When Taj is proposing the challenge to Charlotte the close up shots of him show him facing straight on standing square, but the distance shots he is standing at about a 45 degree angle to her looking to the right to talk to her, not facing straight on to her. (00:35:20)
Continuity mistake: When young Kostya is standing on the table with the jump rope tied round his neck, its knot repeatedly changes position, from Kostya's front to his back.
Continuity mistake: When Sheldon takes his son to school (right after the family picnic where they all heard him claim Ryan as his lover), in one shot his son takes his seat belt off, then two shots later when the son is going to get out of the car, he takes the seat belt off again.