Factual error: When Dora and Paul walk into find the newborn baby kitten on the floor, it shows what a kitten would actually look like if it was newborn. However, after they save it and are with all the kittens later on, the kittens are walking around and they have their eyes open. Kittens don't open their eyes or walk for at least 2 weeks after being born. In the movie, they had just been born.
Factual error: When Paul goes to rent a movie, his first words to (David Spade) are about what movie to rent. When (David Spade) vetoes both of Paul's choices, he offers him a third, which Paul accepts and then leaves. Not once did (David Spade) ask for an ID or video rental card. He didn't even check the movie out of the store's inventory.
Factual error: The movie is set in New York, but after Mena Suvari meets Zak Orth in the convenience store and he invites her to the party, they walk past a line of people waiting to see the Rocky Horror Picture Show. They're standing outside Lee's Palace, which is a) a music club which doesn't ever show RHPS, and b) in Toronto.
Continuity mistake: When Paul goes to get pizza and a movie for Dora, the movie messes up the order that he gets them. First, he goes to the pizza place, and picks up a pizza, you can clearly see him holding a bag. Then, he goes to the video store (with a cameo by David Spade), he has nothing in his hands. Then, he has both after.