In the attack scene in Charley's bedroom, Jerry Dandrige has his hand around Charley's neck and Charley drives a pencil into the top of his hand. In the next scene, Jerry pulls his hand away and looks at the pencil, and it is sticking more than halfway through his hand. If the pencil has been shoved that far down, it would have pierced Charley halfway through his neck.
The holes in Evil Ed's neck disappear after he shows them to Peter.
When the Jerry Dandrige bat-creature is attacking Peter Vincent, it scratches the left side of his face. When Charley Brewster pulls the bat off him, the scratches are gone.
In one scene, Jerry Dandrige appears in the Brewster house. In the next shot, it is revealed that he is standing in Mrs. Brewster's bedroom watching her sleep. However, the first shot was actually filmed in Charley's room. The Ford Shelby Cobra poster on Charley's wall can clearly be seen over Dandrige's shoulder.
When Evil Ed gets touched by the cross on his forehead, the blistering burn is over his left eyebrow. However, in later shots after Peter stakes him, the burn is in the middle of his forehead.
In the opening scene on the television, when Peter Vincent announces his name and goes to impale the vampire with a wooden stake and mallet, his stake is backwards as he rushes in. This was intentional as Roddy McDowell is parodying bad films/actors.
After Jerry Dandrige attacks Charley and runs out of his room, he closes the window that had been nailed shut. After Charley's mother leaves his room, Charley sits down next to the window and it is open again and the curtains are even blowing in the wind.
Charley is actually closing the hallway window Jerry escaped through, which is right next to his mother's bedroom door. The broken frame from Jerry jamming the door can be seen as they talk, indicating they are in the hallway and not Charley's room. Charley then returns to his room, where his window is still open after his mother goes back into her room.
Charley is actually closing the hallway window Jerry escaped through, which is right next to his mother's bedroom door. The broken frame from Jerry jamming the door can be seen as they talk, indicating they are in the hallway and not Charley's room. Charley then returns to his room, where his window is still open after his mother goes back into her room.
When Jerry stalks Evil Ed through the alley, he casts a reflection in a puddle.
When Evil Ed is turned into a wolf and is crawling on the floor, a line can be seen moving the animal.
Seconds before Evil Ed jumps onto Peter Vincent's back and attempts to bite him, Ed's shoulder is glimpsed in the mirror. A moment later it's established that he casts no reflection.
When the bat creature is flying toward Peter Vincent, a line can be seen holding the creature.
When Jerry is first seen in vampire form, as he draws the shade down before biting the girl, it is clear that while the hand drawing the shade has extended fingernails, the other hand does not.
Vampires cast no reflection in mirrors due to the presence of silver on the back of old-world mirrors. A water puddle (like modern mirrors) has no silver and can/should show a reflection.
When Jerry throws Peter's cross away, the sound of it hitting the floor happens before it does.
When Peter Vincent burns a cross on Evil Ed's head, Evil looks into a mirror before realizing he can't see himself. Just when Ed attacks Peter, you can see the reflection of a crew member and a red ladder in the mirror.
Shadow from the camera operator is visible in the window of Charley's house during credits.
In the scene when Evil Ed transformed into a wolf and was stabbed with a stake, he jumped over the banister and the strings connecting to his wolf form are clearly visible.
Charley is supposedly a fan of vampire movies, but he learns from Evil Ed about things like stakes, garlic, crosses, etc., things which should be familiar even to casual horror fans.
When Vincent raises his cross to Peter the vampire, it doesn't work because, Peter says, Vincent "has no faith." But Vincent had recently successfully used the cross on Ed, so not only did Vincent have faith, but it should be even stronger when he confronts Peter.
When Jerry laughs after confronting Peter and Charley at the top of the stairs, you can see metal fillings in his teeth. Vampires are self-healing and shouldn't have tooth decay.