Einzelposting: South Park - Season 13 (engl. & deu.)

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FACT 1) Professor Chaos’s Narrowed it down to 8 kids.

FACT 2) Mr. Garrison stated that it was one of the students in his class.

FACT 3) Cartman, at the end of the episode, said to Mysterion, “I even said it was you!”, narrowing it down to 4 of those eight. The 4 possibilities are Craig, Kyle, Stan, and Clyde.

FACT 4) Mysterion visited Kyle; This rules him out.
This confirms that it is one of the three folling kids:

1) Stan
2) Clyde
3) Craig

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Evidence from this episode only:

FACT 1) There is slight evidence towards Clyde:
-Mysterion states that this is not his first time watching over the city at night; Clyde is seen sleeping during class, implying that he has been awake all night. The scene specifically focused on him, pointing out some significance in this. No other plot explained this scene.

FACT 2) Mysterion leaves Cartman immediately after Cartman guessing that Clyde was his true identity.

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Evidence from other episodes:

1) Craig's dislike for adventures (referenced in the recent Giant Gerbil Peruvian episode). Craig dislikes adventure, and thus would be unlikely to become a superhero.

2) Stan's acknowledgment of Kyle being the "smartest kid in class". Stan has stated this; Mysterion has stated this. Plus one point for Stan being Mysterion.

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There is also the scene of Mysterion visiting Kyle and asking for help. This scene was not elaborated on, but if the show wanted to, it could reference this to a scene in "The Dark Knight" where another character pretends to be the superhero. In this situation, Stan could have impersonated Mysterion at the end, allowing Cartman and Mr. Garrison to be correct, and at the same time, wrong, leaving the true identity of Mysterion a mystery.

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