Adventure Time Season 9 Episode 14 - Three Buckets Episode Title:Three Buckets.Episode Description:Fern reveals his ability to change his appearance to look just like Finn. Impressed, Finn joins Fern in a dungeon hidden in a mountain. Fern traps Finn in one of the rooms, and reveals his plan to replace him. Finn learns that his robotic arm can do a variety of things, and drills his way out of the dungeon. Finn and Fern fight in a field; Finn tries to reason with Fern, but his robot arm mishears the word "finality" as "fatality" and he destroys him. Finn returns home traumatized, and Jake and BMO comfort him. Meanwhile, Princess Bubblegum's Uncle Gumbald (voiced by Fred Melamed) scoops Fern's still-living remains into a bucket.