Why a duck?

Groucho ... Now here is a little peninsula, and here is a viaduct leading over to the mainland.
Chico: Why a duck?
Groucho: I'm all right. How are you? I say here is a little peninsula, and here's a viaduct leading over to the mainland.
Chico: All right. Why a duck?
Groucho: I'm not playing Ask-Me-Another. I say, that's a viaduct.
Chico: All right. Why a duck? Why a-- why a duck? Why-a-no-chicken?
Groucho: Well, I don't know why-a-no-chicken. I'm a stranger here myself. All I know is that it's a viaduct. You try to cross over there on a chicken, and you'll find out why a duck.
Chico: I no go someplace, I just--
Groucho: It's deep water, that's why a duck. It's deep water.
Chico: That's-why-a-duck.
Groucho: Look, rube. Suppose you were out horseback riding and you came to that stream and wanted to ford over there, you couldn't make it. It's too deep.
Chico: But what do you want with a Ford when you got a horse?
Groucho: Well, I'm sorry the matter ever came up. All I know is that it's a viaduct.
Chico: Now look ... all righta ... I catcha on to why a horse, why a chicken, why a this, why a that. I no catch on to why a duck.
Groucho: Well, I was only fooling. I was only fooling. They're going to build a tunnel in the morning. Now, is that clear to you?
Chico: Yes, everything excepta why a duck.

Marx brothers - Coconuts - genius