Freeze up.

You find yourself unable to move or even breathe as the Koopa fondles your thigh, massive hand moving further up as he leans in closer. You know you have to do something, anything, but can't, even as you feel the tip of his cock poking your side. He lets out another throaty chuckle, clearly savoring how helpless you are, and guides your hand to his monstrous member, which is already oozing precum. It's clear what he wants you to do.