Too much sugar
This could be a Lydia Davis story in another universe (from James Maliszewski's Grognardia):
MANY ELVES (Roll 1D20 three times):
1. Have never known another of their kind.
2. Have hair of white or silver.
3. Become intoxicated if they consume too much sugar.
4. Have shadows that seem "alive."
5. Sleep standing up -- and only for an hour or two each day.
6. Claim to have visited other worlds.
7. Call all non-elves "ephemerals."
8. Periodically spend all their funds on worthless baubles that they soon tire of and give away.
9. Devote themselves to a single weapon and will never even touch, let alone wield, another.
10. Can determine if a person is a magic-user simply by sight.
11. Consider silver more valuable than gold.
12. Find the concepts of aging and death endlessly fascinating.
13. Believe politeness is a form of dishonesty.
14. Disappear on the night of a full moon.
15. Refuse to accept magical healing or any other clerical spells.
16. Engage in conversations with beings others cannot see.
17. Are superb mapmakers.
18. View dwarves with strange interest.
19. Will not allow non-elves to watch them eat.
20. Refuse to sign their name to any document.
UPDATE: Sarah has found an important corollary.