Starbucks Vaudeville

It's the joke that just doesn't get old:

Tourist: What kind of berry is a triberry?
Barista: What?
Tourist: You're selling a triberry muffin. Well, what's a triberry? I've never heard of that before.
Barista: It has blueberry, strawberry, and raspberry in it. They call it triberry because it has three kinds of berries in it.
Tourist: So there aren't any triberries in it?
Barista: No.
Tourist: Then why do you call it a triberry muffin? That's false advertising.
Barista: As I explained, it's called that because it has three berries in it.
Tourist: But none of those berries are triberries?
Barista: No. There is no such thing as a triberry.
Tourist: I don't understand.
Barista: Look, do you want the muffin or not?
Tourist: I don't think so. I don't want to eat anything unless I know what it is first.
Barista: So what can I get you?
Tourist: Do you have a donut?
Barista: No.
Tourist: Never mind. [leaves]
Barista: Dumbass.