In the party scene where Julie first meets Randy and Fred and the two guys are kicked out of the party we see Julie standing inside the house looking out the window. From the outside it shows her closing the shutters but when it switches back to Julie on the inside of the house, she hadn't closed them yet.
When Loryn, Stacey, and Suzi meet Julie at Du-par's, Stacey's books are already on the table when Julie begins to speak. When the camera pans over to Stacey, however, she is still holding her books; it is only after then that she lays them down.
When Randy and Julie see each other from across the room, a blond boy in an orange shirt walks from right to left behind Randy and Fred. Seconds later, the same boy walks in the same direction behind Randy and Fred again.
Throughout the party scene, there are instances of kids being in more than one place at a time, depending on the camera view. For example, a brown-haired boy in a gray sweater vest is shown dancing; when the camera view changes, however, he is standing (and not dancing) in a different part of the room.
The opening scene supposedly takes place at the Sherman Oaks Galleria, but the sign on the door from which Julie and her friends leave the mall indicate that they are at the Del Amo Fashion Center, which is located in Torrance, California.
When the girls are dancing to "Girls Like Me" at Suzi's slumber party, the album spinning on the turntable clearly has an A&M Records label on it, but the album that contained that song at the time was actually released on Slash Records.
When Julie and Tommy are at Du-par's, he puts his bracelet on her wrist, but because he does not properly fasten the clasp, one end of the bracelet clearly falls open on the table. Deborah Foreman has to obviously keep her wrist rigid on the table for the rest of the scene in order to keep the bracelet from slipping any further.
When the teacher is giving her speech before introducing the prom king and queen, she takes her glasses off and keeps them off for the rest of her speech. During the shots where Randy and Tommy are fighting, however, the teacher is shown in the background with her glasses on. The teacher's glasses are still off when the curtain pulls back to reveal Randy punching out Tommy, but right before she faints from the sight, her glasses are back on her face.