What is Grimace?

What is Grimace?: "The question is pretty short and to the point. What exactly is Grimace, the McDonald’s character? I mean Ronald McDonald is a clown, that’s pretty clear. And the majority of the remaining McDonald’s characters seem to have at least a passing resemblance or relation to McDonald’s food. The Hamburglar is a thief that steals hamburgers. Birdie is a giant bird. Not sure if she produces the eggs for Egg McMuffins or has some relation to Chicken McNuggets, but she’s pretty clearly a bird. Mayor McCheese has an enormous cheeseburger for a head. The Fry Guys look like a wad of French fries. Well, really they look like pom-pons, but at least the have some relationship to french fries, its in their name. Grimace? I guess he likes shakes. Or are they called partially gelatinated non-dairy gum-based beverages?

But what is he?"