Ash was a minor villain in Adventure Time.
He was a Wizard who was Marceline's immortal ex-boyfriend. The reason for the break up was because he sold her teddy bear Hambo to a witch so he could get a new Cherry Blossom Wand. He later disguises himself as the Rag Wizard, and dopes Finn and Jake into helping him obtain the memory of Marceline dumping him in the pretense that she put herself in a sleeping spell, and would remain asleep for eternity if they didn't get the memory. When they return the memory to him, he destroys it, so that Marceline wouldn't remember dumping him. He then goes into Marceline's house and asks for dinner. He later returns when Marceline's memory comes back to her, and of the bat asks her for a sandwich, not caring in the slightest for trading her teddy bear in exchange for the wand. Finn, Jake, and Marceline then dogpile on him, Marceline kicks him in the groin, and Jake finishes it by forming a humongous foot and stomping on him. He only appears in the episode "Memory of a Memory."Adam Muto confirmed he is still alive.
He made a brief cameo in the Season 5 episode "Betty" in which he appeared in the Wizard City and talked badly to the reformed Ice King/Simon. Simon then punches him off his flying carpet, and he rides it to his Ice Kingdom in hopes of contacting Betty.