Other mistake: When Brian takes a picture of his friend Doug on the boat, the picture shows Doug in a different position than that of when the picture was taken. (01:21:30)
Other mistake: Pay attention to one of the early innings of the baseball game as one of the Angels players hits a home run. Though probaby intentionally set up this way as to avoid any problems of "logo patents" and such with the real life MLB California Angels team, he is wearing a helmet without the team logo on it. (01:07:35)
Other mistake: Nuke is having a great game. Crash comes out BEFORE the first pitch to the next batter and instructs him to "throw the next one at the mascot." Nuke does. Crash tells the batter not to dig in because he doesn't now where it's going, etc. The next pitch is a strike (making the count 1-1), yet everyone cheers and Crash throws down to 3rd base like it was a strikeout and the batter walks away.
Other mistake: When Lea Jansen and Dave Ryder want to leave the room, which is called the "deep freeze", they hear Kalgon and his men coming and "hide" next to the door. When Kalgon and his men enter, the movie wants to tell us that they cannot see Lea and Ryder, although they are obviously in their field of view.
Other mistake: There's a chime hanging outside Salvatore's bedroom window that's too far away to cast such a small shadow over his face when he lies in bed and thinks of his childhood. (00:05:40)
Other mistake: Josh's birthday, according to the milk carton, is in the winter. But, some time after he celebrates his birthday at the Italian restaurant, he returns to his childhood neighborhood and it's fall (colored leaves, etc.). It can't be the following year because he's only gone for a total of a few weeks.
Other mistake: When Jack stumbles into the wrong bedroom, he witnesses Mary's murder twice. Later, Mary reveals that she gets murdered only once every night.
Other mistake: The two headed monster's heads are pretty big. Big enough to swallow a person whole. But when Val Kilmer jumps on one to impale it, the sword comes out of the bottom of the monster's head. For this to happen, the sword would have to be unbelievably large, larger than a man, which he would be unable to wield anyway.
Other mistake: Right after Heather Duke and Heather McNamara drop in on Veronica and Betty Finn playing croquet, Veronica talks to her parents about the suicides. She still has a croquet mallet in her hand, so little time can have passed. Heather Duke rushes in with a shopping bag, and tells Veronica that while at the mall they heard about Martha Dumptruck's suicide attempt. But Heather Duke had just left Veronica's house - there wasn't enough time for these events to happen.
Other mistake: When JoJo is babysitting Phoebe, Kat and Tim run in from the rain. His arm had been around her briefly but when she is in the doorway, he is behind her and both his hands hold up a raincoat. JoJo had made up an excuse about Kat's mother being ill to cover for Kat and Tim's absence. Kat and JoJo leave and have a discussion in the car about whether Tim's wife knows about them. JoJo says "So he had his arm around you, so what, right?" But JoJo had not seen his arm around Kat.
Other mistake: Mr. Phillips told Michael (Danny) that he'd like to hear him play on his "Steinway at home", but didn't say when or give Michael his address, but Michael was able to ride his bike to the Phillips' house. Michael was in this new school (and State) for only one day, so it seems unlikely that he'd know where Mr. Phillips lived. (00:26:33)