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.
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.
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.