Stupidity: When Christine is told that to remove the curse, all she had to do was give an envelope with the button inside to somebody else and that individual would go to hell. She decides to go to the cemetery where Ganush is buried and places an envelope into her mouth. Had Christine actually bothered to check inside the envelope first to see if the button was inside, she would never have gone to hell.
Stupidity: The type of steak that Clyde demands has a sharp kind of bone inside that can easily be used as a weapon. No prison would be foolish enough to overlook this fact, especially as the warden had everything double-checked.
Stupidity: The characters wish for the resurrection of just one person (Roshi) rather than everyone killed by Piccolo as would be natural (and as they do in anime and manga). Okay, Piccolo in this movie sucks at killing and resurrecting Muten covers 50% of the total body count, but they can't know that.
Stupidity: Having become the leader of the universe's most stealthy fighters, he promptly leads them in a Custer-esque noisy frontal charge into a force with known weapon and technology superiority. Zero effort to utilize ANY of their amazing stealth, just have them slaughtered so badly that the planet has to sacrifice animals to save them from extinction.
Stupidity: In the opening scene, when Jason lunges at Whitney, the screen cuts to the title card with his machete swinging 12-6 just inches from her skull. This makes it hard to believe he had a change of heart and pulled his windup before splitting her head in half.
Stupidity: Rescuing Manfred and Diego from the giant carnivorous plant, Buck could have cut both wires simultaneously to avoid that unnecessary horrible potential outcome of cutting the wrong one. The wires were stretchable enough for them to have been held together to then get cut at the same time. (00:37:40)
Suggested correction: Cutting both wires simultaneously would probably cause a different effect. Besides, Buck isn't very intelligent.