Stupidity: When the Turtles are leaving the junkyard they rescued Raphael from, the incredibly agile ninjas of the enemy clan can't simply jump over a van, or just slide over the hood. (00:54:00)
Sammo
Suggested correction: Remember at the beginning of the film, one of the clan members is angry that so many of their members were arrested. They have been looking hard for new recruits. The new recruits won't be as good right away.
LorgSkyegonI am sure even my mom could slide across the hood of a parked car if need be.
Sammo
Stupidity: The Foot Clan knows that April O'Neil is an ally of the Teenage Mutant Ninja Turtles. Since the Foot Clan hasn't been able to find the Teenage Mutant Ninja Turtles for where they live a easy solution would be for them to go to April and ask where are the Teenage Mutant Ninja Turtles. An explanation is never given in the movie for why the Foot Clan never use that easy solution.
Athletic JasonStupidity: Leonardo could use his swords to cut the net when Leonardo, Donatello, and Michelangelo are trapped in a net.
Athletic JasonSuggested correction: While trapped in the net, it would have been quite difficult for him to draw his swords from the sheath on his back.
LorgSkyegonWhile that is true, him not attempting to reach his swords makes him look like a fool that forgot he has swords.