When Pam Grier is handling the jawbreaker during the interrogation scene she is wearing long acrylic nails, but isn't wearing them in the close-up shots of her holding the jawbreaker.
In the scene where the girls open the trunk of Courtney's car we can see that Liz is almost completely covered in bruises and her skin is pale, almost white. But as they walk through the pool area and up the stairs you can clearly see that suddenly her skin tone/bruises are completely gone. When they throw her on the bed suddenly the makeup and bruises are back.
When the newly-created Vylette walks into the school hallway for the first time, we clearly see her wearing a pair of coral-colored high-heeled pumps. The shot of her entering the cafeteria however clearly shows her wearing red low-heeled scuffs, then when she's seated the high-heeled pumps are back. (This is not evident in the intended widescreen frame.)
In the scene where Marcie and Courtney are staging Liz's death scene Marcie and Courtney continuously switch positions from the left side of the bed to the right repeatedly.
At the lunch table, Marcie puts her compact away twice.
When Courtney enters the phone booth to call detective Cruz, there is not a black microphone wire hanging out of her dress; there are just matching seams on her stockings.
In the scene where the girls are carrying Liz's corpse up the stairs, when Marcie plops Liz on the bed you can clearly see Liz's eye's blink twice.
When the girls are taking Liz up to her room to make it seem like rape, when they are half way up the stairs you can see Liz's toes move.
In the scene where Marcie and Courtney are staging Liz's death when they put their yellow gloved on Liz's head is turned towards Marcie, then when the scene cuts back Liz is facing Courtney.
At the end of the film when the entire student body is pelting Courtney with corsages, we see several students throwing upwards of five different corsages at her.
When Liz's parents return home and open the front door, if you look in the background you can clearly see that it does not match with a "real outside setting" for the neighborhood. The background is very bright and blue.
Just after Fern has been made over, the girls are sitting at the cafeteria table, and just after Dean sits down, a boom is visible at the top of the screen. (4:3 transfer only)
When Liz Purr is abducted, she has her hands tied in front of her and is still alive when put in the car trunk. At that point, she was perfectly capable of removing the tape from her mouth and spitting out the Jawbreaker before choking on it.