What is Jello Made of?

Gelatin

Next time that frat guy offers you a Jell-O shot, consider this: Jell-O's main ingredient, as I'm sure it's easy to imagine given the name, is gelatin. But gelatin, for those who don't know, consists of the collagen extracted from an animal's skin and (mostly) bones. So if you've ever been told Jell-O is made of "horse hooves," you're partially correct (though actual hooves are not used in the production process). And also probably partially nauseous.
But if you think it's just Jell-O shots you should be avoiding, you're sadly mistaken … you can find gelatin in everything from Gummy Bears to those marshmallow Peeps you get on Easter Sunday. Now perhaps it seems a wee bit less ridiculous when your vegetarian friends turn down the pastel-colored cuties, because (to you're thinking) they're "animals." Uh, well. Yeah, they are actually."