Monster Arm
S01E05 - Airdate: 2015-04-06
Runtime: 30 min
Marco breaks his arm before a karate tournament. Star uses her wand to fix it, but transforms it into a tentacle arm. As Star tries to find a spell to reverse it, Marco begins to like his new powers associated with the arm. However, the arm harbors an evil sentience that intends to take over the world.
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Episode details and rating from TVmaze.