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.

Star and Marco are trapped inside a tool shed by Ludo's army. As Marco tries to fashion something to fight them off, he recounts how he tried to cheer up Star because she left her phone number for her crush, a keytar-playing student named Oskar, but he has not called her back.