Crew or equipment visible: When the farmer goes in his house to get supplies, the prop master is visible inside the doorway as he exits.
Continuity: Before Dave pops the giant clowns nose with his badge, it is clear that his last name is spelled H-A-N-S-E-N on the badge. However, in the credits it is spelled H-A-N-S-O-N
Revealing mistakes: 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.
Crew or equipment visible: When the clown monster is coming out of the toilet you can see the puppeteer's arm.
Continuity: 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.
Revealing mistakes: When people move the hanging bags of cotton candy, they're obviously far too light to hold a body.
Continuity: 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.
Continuity: 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.
Revealing mistakes: 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.
Crew or equipment visible: When the Clown's vessel takes off, you can see a hand pulling it from the ground.