The esteemed Notices of the AMS (January 2005) included an article by Paul Renteln and Alan Dundes, entitled "Foolproof: A Sampling of Mathematical Folk Humor." Below you will find them offering the standard classic involving abstract algebra, followed by a host of variants....Enjoy or Boo & Hiss or even Scratch Your Head in Puzzlement!
Q: What's purple and commutes?
A: An abelian grape.
Q: What's purple, commutes, and is worshipped by a limited number of people?
A: A finitely-venerated abelian grape.
Q: What's lavender and commutes?
A: An abelian semigrape.
Q: What's purple and all of its offspring have been comitted to institutions?
A: A simple grape: It has no normal subgrapes.
Q: What's purple, round, and doesn't get much for Christmas?
A: A finitely presented grape.
Q: What's an abelian group under addition, closed, associative, distributive, and bears a curse?
A: The Ring of the Nibelung.
Q: What's nutritious and commutes?
A: An abelian soup.
Q: What's hot, chunky, and acts on a polygon?
A: Dihedral soup.
Q: What's sour, yellow, and equivalent to the Axiom of Choice?
A: Zorn's Lemon.
Q: What's brown, furry, runs to the sea, and is equivalent to the Axiom of Choice?
A: Zorn's Lemming.
Q: What's green and homeomorphic to the open unit interval?
A: The real lime.
Q: What's yellow, linear, normed, and complete?
A: A Bananach space.