When Cher is taking her driving test, she scrapes against a white car, causing her passenger mirror to be torn off. However, when the DMV proctor asks her to pull over, the mirror is still there and the car is unblemished.
In the mall scene where Tai is held over the balcony rail, when Cher and Christian get off the escalator, Cher is carrying a small purse that matches her dress. When they go to the bench to talk about Christian's black jacket, Cher puts the purse down on the bench next to her shopping bag. Later, Cher picks up her packages, but the purse is never seen again.
When getting ready for Christian's visit, Cher puts on eye make-up, lipstick, and lip-liner. In the next scene, as Dee applies powder to Cher's face, her makeup is missing.
When Christian is first seen standing in the doorway of Cher's class room, a boy in yellow runs by and a girl in blue walks the other way. In the next shot of Christian, the boy and girl are seen again going in the same direction they were going before.
Cher's drink disappears while watching Travis skate.
The day after Tai got her make-over and needs a boyfriend, Cher says that Elton is recently single. Tai then asks who Elton is, when on her first day of school, Cher specifically pointed out who he was. However, she easily could have forgotten his name. Many people take time to learn the names of people they just met.
The debate teacher refers to Cher as "Cher Horowitz," but the name on her report card (viewed when her father is looking at it, after the grades have been changed) is "Cher Hamilton." The piece of mail her father tosses aside right before looking at her report card says "Melvin Hamilton" also. (Arguably deliberate, see trivia.) In any event, Horowitz is accepted as the canonical name of the characters.
During the driving test scene when the car nearly hits the cyclist and when it sideswipes the parked car, a stunt double with brown, swept-back hair is driving.
When Summer is carrying the snowman out of the party to her car and is holding it, you can see the extension cord that the snowman is plugged into, but it's still lit when she shuts the door and the cord is hanging out the window. It is also still lit when she drives off.
When Travis accidentally "spills" the beer on Cher's shoe during the Val party, nothing is actually spilled from the cup even though there is a sound.
When Mel and Josh are sitting at the dining room table working on documents for Mel's case, Cher comes down the stairs in her white dress. She is first seen at the top of the stairs, then the camera switches to Josh, who apparently is watching her walk down the entire flight of stairs. However, from where Josh is sitting, he can only see the bottom few steps and could not watch her descend the entire staircase.
When Tai and Cher are sitting at the table after working out, Cher says "...for a couple of hours." but mouths "...or something."
Some of the crew and director Amy Heckerling can be seen (briefly) reflected in a shop window through which Cher is looking.
While Cher is by the phone, waiting for Christian to call, the shadow of a camera can be seen moving down the wall.
When Elton's shoe hits Tai in the head at the Valley Party, a crew member's hand who is obviously throwing the shoe from out of shot can be seen quickly on the left (in the wide screen edition).
When Cher and Dionne are driving to school, at one point the shadows of the crew, the camera rig truck, and boom microphones can be seen on the hedge behind Dionne. Once the Jeep turns the corner and Dionne lectures Cher on the importance of Stop signs, the shadow is no longer visible.
When Cher calls Josh using the pay phone she dials the number without putting in coins. Also, Josh hangs up the phone without knowing exactly where she is in Sun Valley.
Near the end of the film, Cher gets upset after flunking her driver's test and storms out. She walks along until she sees a clothing store, and purchases clothing. But she clearly left the house with no purse and wearing a mini dress. How did she pay for the clothes?
When Cher is robbed and her cell phone is stolen, she says that she couldn't call Dionne because she didn't know the number to the party. But Dionne has her cell phone since she took it out to call Murray's mother. So Cher wouldn't have needed the party house's number or to call Josh for a ride.
When Cher is outside Circus Liquor, she says that she's in Sun Valley. Circus Liquor is a famous landmark in North Hollywood.
When Cher and Dionne are reading the card, they wrote to Ms. Geist, Dionne's speaking line does not match the words written in the card.
Under the Teacher's Comments on Cher's report card, Mr. Hall misspells the word "undisciplined" as "undiciplined."
(at about 10:00) When Cher is describing her efforts to get her grade changed in P.E. from a "C" to a "B", the camera pans past some cheerleaders. The second-to-last cheerleader's skirt is caught on her pom-pom, fully revealing her pink panties.
Under the Teacher's Comments on Cher's report card, Mrs. Stoeger misspells the word responsibility as "reponsibility."