Is much likely if the creator didn't came up with the idea, it didn't get made, but sometimes he gets all the credit for it. I suppose it happens with Disney, since most people assumes Walt Disney did everything in his works even if he didn't create very much on it. Same perhaps with other shows like The Simpsons and Sponge Bob?judging by the credits the creators don't seems to be very involved with the actual show run, but the signature of some is the only that appears everywere.