From the Straight Dope, answers to the Mad Hatter's riddle, "Why is a raven like a writing desk?"
* Because the notes for which they are noted are not noted for being musical notes. (Puzzle maven Sam Loyd, 1914)
* Because Poe wrote on both. (Loyd again)
* Because there is a B in both and an N in neither. (Get it? Aldous Huxley, 1928)
* Because it slopes with a flap. (Cyril Pearson, undated)