That wasn't the point of the joke. The point was they couldn't use the name of Disney characters and risk copyright infringement. The original dwarves in Snow White had no names, but Disney named them. One of them was named Doc, but The Simpsons obviously can't use the name Doc because of copyright infringement which is why they said "Doc...tor Hibbert." I'm not saying it was funny or anything, but you should at least know what you're complaining about.