The back doors on Billy's van are closed when he pulls out of his driveway in one shot. When the cops pull a U-turn and question him, the shots through the windshield of the van reveal that one of the van's back doors is open.
Kathy asks about the mark on Billy's chest when she and Billy are lying next to the van. When they go to the pool party, it's gone. Later, Billy shows the mark to the police, and it's clearly visible as a silver "spot", but then when he goes on his final rampage all over the town, it disappears several times.
When Billy first visits Kathy's house, he puts on his shirt just after he gets out of his van. In the next shot, as he gets to the front yard, he is carrying his shirt, which he puts on as he enters the yard.
When the "alien cops" arrive in the desert, the First Humanoid Alien stands up from behind a shrub. In the next shot, he is still crouching. A few shots later, he stands up again.
When Billy first finds the laser and figures out how to shoot it, he puts the amulet around his neck and continues to shoot. When he is shoots after he dons the amulet, he is still holding it in his hand.
When Billy blows the hippie out of the VW van, the hippie falls out the open door, which has suffered no damage. However, in the next shot, the door is missing, and the side of the van is scorched.
Near the beginning of the film, when the police take off in pursuit of Billy's van, their tires squeal on the dirt shoulder.
In a shot of the van from the front, after Billy blows up the Star Wars sign, the camera rig is visible on the left.
After Kathy has finished looking at Billy's pendant, and Billy wakes up, the edges of his monster makeup are visible around the top of his nose.
A stunt man, in full fireproof gear and helmet, is visible when Billy blows up Chuck and Froggy.
When the camera dollies around the gas pump when Tony Craig stops, the camera is reflected on the glass.
When Chuck and Froggy's burning car is rolling along in slow-motion, cables are visibly streaming from the rear of the vehicle.
At Dr. Mellon's crash site, the boom operator is visible in Tony Craig's car door.
The boom mic dips into frame when the Sheriff calls Deputies Unger and Jeep into the office.
In the exam room when Dr. Mellon tells Billy he's going to give him "a local", the boom mic is visible.