When monks illuminated manuscripts in the scriptoria of all of those Benedictine monasteries across Europe back in the day, they often drew odd, funny, and just plain weird little pictures in the margin. And it turns out that they really liked drawing pictures of knights fighting snails.
I saw this write-up the other day, and was going to post on it in due time, but Tom McDonald beat me to it (and did a better job than I would have). So go look at his post. And be sure and click through and look at the pictures.