Movie moments

I am horrible at remembering specifics about a movie when one particular line sticks in my mind. And being as how this movie is a part of a trio, I fear I may have listed the wrong movie. But I'm pretty sure it was this one.

The main character is trying to convince one of his good friends to do something with him, and his friend tries to avoid doing it. So he asks him, "Are you a Mexi-Can, or a Mexi-Can't?"

I thought it was pretty funny.