Organic chemistry textbook: The rhinoceros is a hybrid of a unicorn and a dragon

Analogies are tricky things. One minute, you're trying to find a clever and memorable way to illustrate molecular bonding of hydrocarbons ... the next you're suddenly Napoleon Dynamite and all your zoologist friends are yelling at you.

This image, apparently taken from a real textbook, is part of an excellent Tumblr blog of textbook fails called "Thanks, Textbooks". You should check it out.