Small is Tall.
Hee. I have to admit to having had a similar conversation once, though it was at the movies.
Guy at the snack counter: Okay, a small? *Hands me a coke that is so wide, my hand can barely hold it.*
Me: Um... do you have any... thinner cups?
Guy: Our medium! *Hands me a cup that, were it on the floor, would reach my knees*
Me: I - need it a lot smaller than that, I'm sorry.
Guy: *Hands me a really small cup with pictures of Dora the Explorer on it*
I must say though, this girl did sort of seem to be making it a bit harder on herself at the end. I know, I know, it's only a video - just saying. ;)