Maybe there's something cultural that's lost in translation, but it turns out the illustrators of medieval manuscripts often enjoyed adding odd, funny, or grotesque images around the text. Discarding Images is a tumblr dedicated to sharing the oddities.
For example, a bunny playing a trumpet:
A man who's not happy about a cat's grooming habits:
And what's described as a "monkey prank." I'm glad I don't know these monkeys.