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)
LorgSkyegon
Upvote valid corrections to help move entries into the corrections section.
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.
Stupidity: Leonardo could use his swords to cut the net when Leonardo, Donatello, and Michelangelo are trapped in a net.
Upvote valid corrections to help move entries into the corrections section.
Suggested correction: While trapped in the net, it would have been quite difficult for him to draw his swords from the sheath on his back.
While that is true, him not attempting to reach his swords makes him look like a fool that forgot he has swords.