Of course I'm not allowed to edit Wikipedia, but if I were, I might have recently been presented with this CAPTCHA image when saving an edit with external links.
(IMG:http://i245.photobucket.com/albums/gg59/writerjudd/IMG_0303.png)
Gratuitous, yes. But I'll admit to laughing every time I look at it.

(By the way, I suspect it's supposed to be a combination of "heads" and "hits".)