The Grim Adventures of Billy & Mandy

Billy Idiot (4x23)

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When Billy is accepted to Mrs. Pollywinkle's dancing academy, his father tries to persuade him to forget about dancing because of his own bad experience as a child during a recital. Then, at the academy, it is revealed that Mrs. Pollywinkle is actually a powerful, dark witch set on stealing Billy's soul. Then, Billy's dad unexpectedly comes to rescue, challenging Mrs. Pollywinkle to a dance competition, which he wins using a powerful dance move. In the end, Billy's dad tells Billy to follow his dream of becoming a dancer if he so wishes, but Billy changes his mind saying that dancing is for girls.