Go to the scene after which Big Mouth (Morton) asks about what kingdom they should conquer next. Mario surprises the Koopas and demands they "let Luigi, Princess, and Toad go and turn Prince Hugo the Poodle back into Prince Hugo the Huge or else." After King Koopa commands the giant Koopalings to grab Mario, the shot cuts to a shot of Toad, Princess, and Luigi (in that order) in the cage. In that VERY shot, look at Luigi. His hat (along with the L) and overalls are now red, like Mario's!!! They're supposed to be green! Maybe the color-in people got lazy, but the art director should've noticed this!