Gaffes

Despite the funhouse being a portable carnival attraction, it has a basement.

When the magician gives his "history" lesson prior to the performance, he references Vlad the Impaler. He says that he ruled Wallachia in the 5th century and he called him Vlad the Fifth. In truth, Vlad the Impaler was Vlad the Third and he lived and ruled during the 15th century.

When the "monster" hands the cash to Madame Zena so she'll have sex with him, the bills make the crinkling sound of ordinary paper, not the sound that real money makes from being made from cotton and linen fibers.

Amy and Buzz leave her house in a 1966 Pontiac LeMans (obvious because of the grill and chrome badging behind headlight). The deep recess in the top of the c-pillar indicates that it is a convertible. Moments later when they are going down the road and even more clearly in the carnival parking lot when they are parking, it is a 1967 Pontiac GTO with a black vinyl top (notice the different grill insert and blinkers, as well as missing chrome badges on fender).

The knife at 1:16:00 is obviously made of rubber.

Near the beginning of the film, after Joey scared Amy and she chased him into the bedroom, she told him she wasn't going to take him to the funfair on the weekend because of it. Nearer the end, the Funhouse Barker says that the funfair is packing up in the morning and moving on.