Revealing mistake: When the gang tries the growth formula in the theatre, they quickly grow out of all their clothes until they are naked. But the scrunchy in Jean's pony tail is still in place and shows no signs of being stretched, even if the pony tail now is 20 times bigger.
Revealing mistake: In the dance hall scene, you can see the wires attached to the ducks to make them move.
Continuity mistake: When one of the kids break into the laboratory, everyone else is partying in the garden. In the outside shots, it is dark, but in all the shots from inside the lab you can see through the windows that it is daylight outside.
Plot hole: The giant-sized teenagers show themselves at the garden party and start making threats about taking over the town. They then spend the night in the theatre, and the next day they decide to cut off all communications to and from the town. For some reason, not one of the party-goers, or the sheriff, decided to call someone during the night and tell the remarkable story about 30 feet tall teenagers seizing the power through force.
Revealing mistake: When the teens are at the theater for the first time, one of the teens on the right leans on a statue that bends after he leans. He then looks over quickly and stops leaning. He then looks sheepishly at the camera.
Revealing mistake: When the girl on the motorcycle is trying to tie Mike's legs together by driving around them in circles, his legs are obviously props. This also goes for later, when he is lying on the ground and the townspeople are trying to tie him up. When his legs are in shot, they look fake, and never moves an inch.
Continuity mistake: When Mike fights the giant spider in the basement, he floods the basement and electrocutes the spider. Later that same night, the teenage gang break into the basement, but there is no sign of neither the water nor the huge, dead spider.
Continuity mistake: When Wolf first grew to giant size, he had trouble fitting through a door because of his size. Toward the end, though, he is sitting at eye-level with Genius and has become much smaller. This is before Genius makes the gas that would shrink him back to regular size.
Deliberate mistake: The theatre is said to have been closed down "years ago". But all the theater props are still there, and the place shows no sign of disuse, it is not even dusty anywhere. The electricity and water are also still hooked up and functioning.
Continuity mistake: During the barbecue, Mike's hair is at first very high. In between shots while in the garden, his hair constantly varies in height, and when he goes into the basement his hair is almost flat against his head.
Deliberate mistake: When trying to capture the giant Fred, the townspeople trip him with an outstretched rope that they hold in their hands and is not fastened to anything. He is the size of a lighthouse, there is no way they could have held a rope in their hands and tripped him with it.
Other mistake: Toward the end, Genius and Wolf (the dog) are in the lab, Genius suddenly shouts at the dog, "Hey, don't do that. Keep away." The dog wasn't doing anything except wiggle his ears a little. He made no move whatsoever toward the glass jar Genius wants him to stay away from.
Other mistake: When the teens first grew into giants, their clothes did not grow with them, so they had to make improvised clothing out of theater curtains. In the end, when exposed to the shrinking gas, the teens become their regular size, and the improvised clothes also shrink with them. No one else's clothes are affected by the gas in this way.
