Factual error: In the DJ spin-off scene, Zach and Francessca help make Meeker cool by going into hypertime and giving him a dance lesson. At one point, we see Zach and Francessca in hypertime making Meeker do flips. Then, in real time, we see that Meeker is doing the flips at the same speed that he was doing in hypertime. Wouldn't he be going a lot faster in real time, not the same speed as he was in hypertime?
Other mistake: After Zak and Francesca get through the giant fan, Zak unscrews the vent cover and it drops like a rock, but as the camera pans out you can see that everyone is still frozen. So, wouldn't that mean that the cover is supposed to look like it dangles in mid-air and be in normal time? (01:13:54)
Other mistake: When the young couple goes into town everything is moving very slow, almost as if they are frozen. When they are looking at the Mustang, look in the background. The guy standing still has become a victim of wind. Notice his shirt flapping in "real time" and not "hyper time". If everything is slow then how come the guy's shirt is blowing in the wind?
Character mistake: Early in the story Dr. Gibbs rationalises the story to come by using two cars traveling the road at greatly different speeds to illustrate "Einstein's theory of relativity". He basically says that the slower moving car seems to stand still as seen from the much faster car's point of view. But in real Einsteinian relativity, just the opposite happens. When two reference frames are traveling with respect to each other, each sees the other's time advancing more quickly.
Factual error: At the end Zak enters double hypertime. He cannot touch the table and can walk through the wall because his molecules are moving so much faster than the molecules of the solids. If this were true, the solid floor molecules would not be able to hold him and he would fall under. Where he would stop, I don't know.
Continuity mistake: When the main character goes to visit the foreign girl she puts him to work raking leaves. Seeing the amount of leaves all over the lawn he puts into action a plan to quicken the task. Later we see a bunch of piles of leaves all over the yard. While speaking with the girl you can see the piles of leaves in the background. At one point, as they are speaking back and forth, the lawn has leaves spread out all over it. Then, as they continue to speak back and forth, the leaves are once again in neat piles.
Revealing mistake: Just after Zak realizes the power of his watch, he and Francesca ride off into the town square and pass a Los Angeles transit bus. In the same town later that evening, as Zak and Doppler are being pursued by the evil operatives, they disengage the hyper-time, and just barely miss a head on collision with a New York MTA bus. (00:33:15 - 00:48:55)
Other mistake: When Zak is trying to sell his father on co-signing for the '65 Mustang, he talks about putting a V8 in it. As evidenced by both the first look at the Mustang's V8 emblem on the used car lot, and the last look when he revs the motor at the end of the movie, the Mustang already possesses a V8.