160px-Billy old
Billy is a character who appears in "His Hero". Billy is Finn and Jake's idol and the most powerful hero seen in the series. Thus, the two are immense fans of him.

As described in "Billy's song", when Billy was younger he was a hero of action much like Finn. he is known to have rescued a princess from Fire Count, slain an evil ocean, and fought against a giant bear. Perhaps most importantly, he is said to have defeated The Lich.