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.