Chopped Junior (2015)

S5E46 Rattleballs

Finn hones his sword fighting techniques in the whimsical candy junkyard, where he encounters an ancient gumball robot known as Rattleballs. To his surprise, Finn realizes he’s far from the skilled swordsman he believed himself to be. Eager to improve, he pleads with Rattleballs to become his mentor. However, Finn soon uncovers a troubling secret about his new trainer, one that will challenge his loyalty to Princess Bubblegum in unexpected ways.