Though neither characters has been particularly key to the overall arc of the show, both have played major roles at key points in the show's run. Dr Hibbert is a dependable background character, functional in medical situations but with enough of a personality to make him more than just a story spinning mechanism. His appearances usually coincide with Homer's moments of weakness and lack of self-restraint, which usually makes for richer episodes as a rule. Bleeding Gums meanwhile is responsible for making Lisa Simpson a far more interesting character: rather than just being the snarky outsider, her backstory was fleshed out hugely by the appearance of her idol. He was her anchor to relatability and their moments of connection were always remarkably touching.