Hey, my stars turned into grotesque grinning faces when I reached 2001 posts! It also says "I'm sorry, Dr. Novella, I'm afraid I can't do that."
(They've probably changed back now)
Edit: Yes they have changed back. When do I get my next Easter Egg?
It's a pity that the post count updates on all messages and not only on the one it applies to. I would have liked to keep that.
Edit Edit: Seems I can keep it ...