Cartoon was probably a loose definition, so I'll change it. How do you do a caricature of a model, not a real person that developed on it's own, that was in all probability created from a drawing. A play on its features when the model was a play on fictitious features to begin with that were already exaggerated for comic affect. Unless, of course, one had met the actual, real life Gonzo. You know the one that exists in nature so you could play off his distinct features. Then it would be a caricature. Otherwise it is just a drawing of a drawing of a character that doesn't really exist. See, what I mean. Whatever, one draws will be exactly how that character looks like at the time it is drawn.