Groucho Set Theory
Groucho Marx's famous quip creates a Russell's-paradox-style contradiction, to Bertrand Russell's dismay.
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Cartoon by Ben Orlin, Math with Bad Drawings. https://cartoons.mathwithbaddrawings.com/2018-12-27-groucho-set-theory/ (CC BY-NC 4.0)Transcript
Groucho Marx: "I don't care to belong to any club that will have me as a member."
[Board] Venn diagram: "Club of All Clubs" containing "Clubs to Which Groucho Belongs" and "Clubs to Which Groucho Cannot Belong"
Bertrand Russell: "CURSE YOU, GROUCHO"