We don't have franken berries either

Nancy Friedman at Away With Words posted this exchange that she found at Overheard in New York.

Someone going by the name Waplow submitted this--overheard at a Starbucks:

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.

What's my commentary? Brand names? Taking things literally? Ambiguity?

Actually I'm going to ignore the exchange for now. What I first noticed was an implication about the players. A Tourist and a Barista. I wonder what information the 'reporter' had that led to the label Tourist. Was it an accent? Was it a t-shirt that said Hey there! I'm from the Midwest! Was there some sort of announcement?

So let's assume that indeed there was a clear indication that it was a tourist. Why use the label? Why not Customer? Tourist doesn't add anything necessary to the structure of the joke. But there is a definite misoxenic pitch in this. Looking over the archives at Overheard in NY this is not typical. Many of the dialogs that identify a tourist do so when that identity is relevant to the conversation and necessary for the humour. Such as the following overheard on the subway:

Manic tourist lady #1: Oh wow, the front of the train. I've never been in FRONT before. Look! Haha! No driver!
Manic tourist lady #2: No driver? Seriously? Excuse me, sir? Who's driving this subway?

Local looks up from paper and looks around frantically.

Manic tourist #2: Wait, seriously? Oh my God, should we get off?
Manic tourist #1: Oh, calm down. He's just joking. We can't get off 'til Union Square.
Local: Ma'am, I swear to God that I'm not joking. Nobody's driving this train. I'm just as terrified as you are.
Manic tourist #2: Oh, whatever. He's one of those New York assholes we heard about. Ignore him.

--Location: 4 train, 59th St