Santa spends the whole year deciding whose been good and whose been bad. This means he can only have sex the day after xmas, because the next day he must go right back to work again. Mrs. Clause has gone the whole year un-fucked, so at this point, there is much dust in her vagina. Because of all of the Chimneys Santa has gone down, he is not afraid. But because he has been down so many Chimneys, there is black soot and marijuana resine on his penis. When he fucks Mrs. Clause, her dust is replaced with soot and marijuana resine.
Santa's Chimney Dilema is the grossest thing I've ever heard of, I like the Easter Bunny absense of toilet dilema better.