A haddock is best described by this exchange between Professor Wagstaff (Groucho Marx) and Baravelli the Ice Man (Chico) in the 1932 Marx Brothers classic Horse Feathers:
BARAVELLI (through the peephole, behind a speakeasy door): You can't come in unless you give the password.
WAGSTAFF: Well, what is the password?
BARAVELLI: Aw, no, you gotta tell me. Hey, I tell what I do. I give you three guesses. It's the name of a fish.
WAGSTAFF: Is it "Mary"?
BARAVELLI (laughing): 'At's-a no fish!
WAGSTAFF: She isn't? Well, she drinks like one... Let me see... Is it "sturgeon"?
BARAVELLI: Aw, you-a craze. A "sturgeon," he's a doctor cuts you open when-a you sick. Now I give you one more chance.
WAGSTAFF: I got it! "Haddock."
BARAVELLI: 'At's a-funny, I got a "haddock" too.
WAGSTAFF: What do you take for a "haddock"?
BARAVELLI: Sometimes I take an aspirin, sometimes I take a calomel.
WAGSTAFF: Say, I'd walk a mile for a calomel.
BARAVELLI: You mean chocolate calomel? I like-a that too, but you no guess it. (Baravelli slams door. Wagstaff knocks again. Baravelli opens peephole again.) Hey, what's-a matter, you no understand English? You can't come in here unless you say, "Swordfish." Now I'll give you one more guess.
WAGSTAFF: ... Swordfish, swordfish... I think I got it. Is it "swordfish"?
BARAVELLI: Hah. That's-a it. You guess it!