Slave Island - S1-E7
Stupidity: The mutants that are held prisoner and forced to build the dam on Genosha are allowed to keep their costumes on. The prisoners are captured so that their powers can be used to build the dam faster, but there's no reason why they wouldn't all be given prison uniforms. Characters like Gambit and Jubilee are wearing jackets, and Jubilee uses it to her advantage by pocketing a piece of twine to pick the lock to her cell later on.