S9E12: Bart Carny

In "The Joy of Sect," the twelfth episode of the ninth season of "The Simpsons," things get a bit culty in Springfield. The family, along with most of the town, falls under the sway of a mysterious cult called the Movementarians. They promise salvation and a free trip to another planet on a spaceship, which is just vague enough to be enticing. Homer, being Homer, dives in headfirst and becomes a devoted follower. It's not long before he's trying to recruit the rest of his family into the fold. But Marge, ever the skeptic, sees through the brainwashing techniques and resists. She eventually manages to escape from the cult compound and seeks help from Reverend Lovejoy, Ned Flanders, and Groundskeeper Willie. With their assistance, Marge hatches a plan to deprogram Homer and the kids. They infiltrate the compound and manage to break the family's trance-like devotion to the cult. In classic Simpsons fashion, it all culminates in a chaotic showdown where the Movementarians' scheme is exposed as a scam. The episode wraps up with Springfield's residents snapping out of it just in time to see their supposed spaceship being revealed as a rusty old tractor hidden behind some clever props. The townspeople disperse, leaving Homer and his family to return to their usual antics with no lasting consequences from their brush with cult life.