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"Monster Arm" is the fifth episode of the first season of Star vs. the Forces of Evil.

The episode premiered on April 6, 2015, alongside "The Other Exchange Student".[2]


When Marco hurts his arm before a big karate tournament, Star tries to fix it with magic.[3]


At the Diaz Household, Marco trains for an upcoming karate tournament, at which he looks forward to defeating an overprivileged karate student named Jeremy Birnbaum. However, when Marco attempts to break three stacked planks of wood, he breaks his arm.

With his arm in a cast, Marco laments not being able to participate in the tournament. But when he sees Star using her magic wand to experiment with different hairstyles, Marco suggests she use magic to fix his arm. Star pulls out the large instruction manual for the wand from under her bed and looks for a bone-healing spell. Upon finding the spell (which Star mentions is in an ancient language), she casts it on Marco's arm, turning it into a long purple tentacle. Star looks for a spell to turn Marco's arm back to normal, but the tentacle, appearing to have a mind of its own, swats the spell book out the window.

The next day, Marco's "monster arm" starts getting in the way of his daily routine, like smacking his face, making his morning shower too hot, and smacking his breakfast off the table. Despite Star's overnight efforts, she still hasn't found a way to reverse the spell. Later during lunch, Star and Marco see Lars, a school bully, picking on Francis. Marco's monster arm suddenly punches Lars and smacks his face several times, causing him to run away in tears. The other students in the cafeteria hail Marco as a hero, and Marco starts to see the benefits of having a monster arm, especially when Jackie notices him.

That night, Star thinks she has found the reverse spell, but when she tests it on a houseplant, it burns up. She stays up all night trying different variations of the spell until she finally gets it right by morning. She goes to Marco's bedroom, where Marco is doing push-ups with his monster arm. Marco thinks the arm will help him defeat Jeremy at the karate tournament. When Star mentions that the arm would give him an unfair advantage, Marco criticizes her for using magic whenever it benefits her. Star thinks the monster arm is becoming a bad influence on Marco, and Marco pushes her out of the room. Once Marco is alone, the monster arm suddenly starts talking to him, saying Star is just jealous and that he can give Marco everything he's ever dreamed of. Marco falls for the arm's words and agrees.

Later, at the karate tournament, Star sits in the spectator stands next to Ferguson and Alfonzo, exhausted from staying up all night. Sensei Brantley introduces Jeremy Birnbaum, an arrogant kid appearing to be no older than eight, and Marco. When the match starts, Marco makes quick work of Jeremy, using his monster arm to toss him around the dojo. As Marco revels in his victory, the monster arm latches onto Jeremy and encourages Marco to eat his bowels. Marco refuses, so the monster arm decides to devour Jeremy himself. Marco realizes that Star was right about the monster arm and stops him from eating Jeremy. As the arm attacks Marco, Marco tells Star to cast the spell, but she's fallen asleep by this point. Alfonzo and Ferguson wake her up with a splash of water. Star tries to cast the reverse spell, but the monster arm keeps dodging, causing the spell to turn whatever it hits into an arm. Marco uses these arms to keep the monster arm from moving, and Star successfully hits it with the spell. Just before turning back to a normal arm, the monster arm gives Marco a foreboding warning that it's a part of him now.

Marco is thrilled that his arm is normal again. Unfortunately, it's also back to being broken. Jeremy thinks Marco's broken arm means he wins, but a set of golden brass knuckles slips out from under his glove. Because of their cheating, both Marco and Jeremy are disqualified from the tournament. Marco apologizes to Star for not listening to her and wonders what the monster arm's final warning meant. Star says it's "probably" nothing to worry about. The episode ends with a worried-looking Marco and a quick tilt of the camera down to his arm.


Major characters

Minor characters

Production notes


Title in other languages

Language Title Translation
Chinese 怪物手臂 Monster Arm
Dutch Monsterarm Monster Arm
French Tentacule tentateur Tempting Tentacle
German Monströs! Monstrous!
Hebrew יד מפלצתית A Monstrous Hand
Hungarian Szörnykar Monster Arm
Italian Il Braccio-Mostro The Arm-Monster
Japanese ヌルヌルの腕 Slimy Arm
Korean 문어다리 Octopus Leg
Malay Tangan Raksasa Monster Arm
Polish Ręka potwora Monster's Hand
Portuguese Braço Monstruoso Monster Arm
Russian Рука-монстр Monster Hand
Spanish El Brazo Monstruoso The Monster Arm
Thai เจ้าแขนปีศาจ Monster Arm


View the episode transcript here.


Click here to view the image gallery for Monster Arm.
Click here to view the gallery.


  • This episode was released early on, the WATCH Disney XD app, and Disney XD on Demand on February 23, 2015.
  • Nick Swardson stars for the first time as Sensei Brantley.


  • A girl sitting in the audience for Marco's karate tournament looks very similar to Candy Chiu from Gravity Falls.
  • In the beginning of the episode, a poster of "Kung Fu Fellow" is seen on the wall of the room where Marco practices karate. This character is stylized very similarly to Samurai Jack, the lead of the critically acclaimed show of the same name.
    • The title may also be a nod to the Kung Fu Panda film series.


  • Marco has a cast with Star's name and drawings while he is lying on the bed; after he gets up, Star's name and drawings disappear.
  • In the scene where Jackie and her friends are admiring Monster Arm, the blue stripe in Jackie's hair overlaps her left eye, making it partially blue in the corner.
  • When Star finally gets the spell right, the hand has five fingers, while the characters in the show normally only have four.
  • Throughout the final few scenes, the bracelet on Star's left wrist disappears and reappears randomly.
  • In the scene where Marco is fighting the Monster Arm, Star seems to be aware of the situation, even though at this point she should have fallen asleep.
  • The calligraphy at the background of karate is not Chinese, Japanese or Korean, and the "script" is just gibberish signs.
  • When the duel between Jeremy and Marco starts, his monster arm grabs him, which is from the opposite side of the dojo. However, in the next scene, Marco appears in the middle of the dojo.


  1. New Episodes | Super Spatial Sundays | Disney Channel Asia. YouTube (2015-11-17). Retrieved on 2017 March 5.
  2. TV News Desk (2015-03-27). Disney XD Announces April 2015 Programming Highlights. Broadway World. Retrieved on 2017 March 5.
  3. bradmin (2015-02-15). ‘Star vs. The Forces of Evil’ Second Season Ordered Ahead of Series Premiere; Initial Season One Schedule. Stitch Kingdom. Retrieved on 2017 March 5.