The "cotton candy" seems to have acidic properties since it is shown several times dissolving the corpses inside. Yet when checking the prisoners' bodies, Dave is able to pull it off bare-handed with no damage to his skin.
When Joe first looks out of the car window to see the Klown-without-a-car, the clown has no headlights on his feet, but does in all other shots.
When Mike and Debbie run out of the wood toward the car, the balloon dog is missing during the next quick shot of the Klowns chasing them.
In the bathroom scene, before Debbie puts her dress in the basket it's clean. In the next close up shot, it's covered in popcorn.
When Debbie is attacked in her bathroom, the little clowns bite holes in her shirt. Later, when Mike and Dave rescue her, the holes are gone.
When officer Dave returns to the station, the power is out, yet the phones are still ringing, they should not still ring in a power outage.
During the motorcycle gang scene, the clown's zipper is clearly visible behind his hair as he turns around.
When Mike & Debbie first come upon the big top in the woods, Debbie's right arm disappears due to her crossing into the matte shot.
After the Terenzi Brothers fall through the trap door and the others turn around to see them gone, Grant Cramer stumbles and almost trips over them. This is because the actors playing the Terenzi brothers only fell on the floor, not through it.
You can see the clown's zipper in the costume at 33:20 mark. It's the scene where the little clown with the green hair confronts the biker who destroyed his tricycle.
When Debbie is attacked by the clowns from the medicine cabinet, you can see the holes where the puppets are being controlled from.
Though Dave's police badge reads "Hansen", his name is written as "Dave Hanson" in the end credits of the film.
The dialogue with the mother in the fast food restaurant does not match her mouth movements, meaning it was dubbed over by another actress during post-production.
When the farmer goes in his house to get supplies, the prop master is visible inside the doorway as he exits.
When the Klown is chasing the man in the car, he is supposedly floating in the air. In some shots, you can clearly see the black motorcycle carrying him in the air.
In the bathroom scene when the Klown comes out of the toilet to attack Debbie, you can see the arm of a crew member operating the puppet.
When the Klowns' vessel takes off, you can see a hand pulling it from the ground.
All the cars have New York plates, but on the street in front of the drug store has a California Highway 152 sign in a early scene.
When Mooney takes the clown back to put him in a cell, it appears that he is unlocking the cell door, but, there is no key.