Are You Afraid of the Dark?

The Tale of the Ghastly Grinner (4x9)

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Ethan wants to be a comic book artist, but his submissions are constantly rejected by companies. One day, he's invited to a comic shop, where he gets the only copy of the comic ""The Ghastly Grinner."" He accidentally brings the supervillain to life and it starts turning everyone into giggling mindless idiots.