Origin
Doctor Musclebump is a very muscular and well built Doctor who diagnoses Finn as Quest Deficient, and orders for him to go on a Quest with Jake.
Creation
Doctor Musclebump is created by writers Paul Tobin, Colleen Coover and artist Wook Jin Clark. Doctor Muscle first appears in Adventure Time: The Flip Side.
Powers and Abilities
Presumably Doctor Muscle possesses some type of medical degree and medical ability and knowledge. He is also quite well built forearms.