When Dale looks at the photograph taken of her and Kirby, the perspective of the photograph looks as if it was taken by the movie camera (from the profile) rather than from her boyfriend who took the photo, which would be from the front.
When Felicia walks into the bar at the Halloween party, her bow is on the right side of her head. Camera cuts to Alec, then back to Felicia, and her bow is suddenly on the left side of her head.
Alec shows up at Kevin's apartment the morning after Kevin and Leslie have sex and starts talking to him from the living area, unaware that Kevin and Leslie are in the bedroom. Kevin then exits the bedroom wearing a red robe. In the next cut showing Leslie in bed overhearing the conversation, someone wearing a red robe can be seen exiting the bedroom.
In the cafeteria scene when Jules, Leslie and Wendy are in line getting their food, the food on the plates changes spots.
When Jules attacks Billy after getting out of the Jeep, her left earring is missing for one shot, but then reappears in the next shot.
The film takes place at and around Georgetown University. However, various characters in the film are seen wearing red/white varsity letter jackets, the colors of the University of Maryland, where the campus scenes were filmed. Georgetown's colors are blue, gray, and white.
If Kirby and Dale dated when he was a freshman in college and she was a senior, then she would only be in medical school not a doctor as their date was only 4 years prior.
The music of a tenor saxophone is heard the music is clearly that of an alto sax.
In the kitchen, Andrew McCarthy is stirring the vegetables in the pan when Judd Nelson enters carrying a bag under his left arm. Andrew McCarthy asks what's that under your right arm, but it should have been left arm; Andrew has asked it from HIS perspective, rather than Judd's actual right arm.
When Kirby is about to leave the cabin where Dale and her boyfriend are staying, the boyfriend says that he is going to go get the camera to take a photo of Dale and Kirby. Other than to get the boyfriend out of the scene so that Kirby can kiss Dale, this makes no sense.
Billy carries his sax on his back with a shoulder strap connected to the armature. If he were a serious experienced player he would, at the very least, bought a beat-up case from a pawn shop and paid next to nothing. Carrying it like this could easily damage the instrument.
In the beginning, the first time they go to the bar, while they are sitting drinking, Demi Moore (Jules) says a line but her mouth is not moving. The line she says is "except I'll have alligator bags", which is a line she says later while they meet Wendy at the homeless shelter for lunch.
When Billy is playing the saxophone in the bar, when he shakes his sweaty head over the woman near the stage he pulls the mouthpiece out of his mouth before the sax music stops.
When Leslie is at Alec's apartment collecting her belongings, he tells her not to take the vinyl of The Pretender's first album. However the album that she is carrying is clearly "Learning to Crawl," their third album.
Based on Billy's irresponsible, juvenile, and downright stupid behavior, it's impossible to believe that he was able to graduate from a university of the caliber of Georgetown.