After the Driller Killer kills one of Courtney's friends, there is no gore on the drill. Albeit in the next shot, gore is present on the drill.
In the first Slumber Party Massacre, Trish has the last name Devereaux. In this movie, Courtney refers to her as Trish Craven.
After the murder with the yard sign, the killer puts the sign back into the yard - but there's no blood on it.
When the two girls and Jeff escape the house, Jeff's car door - leading to the driver's seat - is ajar. He opens the door to the driver's side and slams it shut; however in another shot, when the three drive away from the house - somehow that same car door is ajar.
While the girls are riding up to their vacation house, the windows on the wagon van are either open or closed.
Jeff's car door is ajar.
When the girls are driving up to the cottage and Courtney is staring out the window, when the camera focuses on her you can clearly see the green screen in the rear passenger's window.
Plexiglass barrier and flammable liquid visible in front of The Driller Killer right before Courtney sets him on fire.
When the killer tosses a severed arm on Trish's cake, a crew member's hand is partially seen at the bottom of the screen used to stick the landing.
When Courtney heads off to school with her friend, the camera crew is clearly visible on the car door.
Camera shadows visible on the floor during the final bits of "Let's Buzz"
The matte box of the camera is reflected on the car window, where Sally and Sheila are sitting.
Courtney makes reference to the events that happened in Slumber Party - O Massacre (1982), saying that she was 12 years old. But we know from dialog in that movie, that she was at least 15 in the first movie.
One of the police officer's name's is homage to "Freddy Krueger". But it's misspelled on his name tag as "Kreuger".