S9E13: The Joy of Sect

In the episode "The Joy of Sect," the Simpsons family gets entangled with a cult called the Movementarians. Homer is quickly brainwashed, and the rest of the family soon follows suit, except for Marge, who sees through the deception. She tries to save her family from the cult's clutches. Marge manages to escape and seeks help from Reverend Lovejoy and Ned Flanders. Together, they stage an intervention and deprogram the kids. However, Homer remains stubbornly loyal to the cult until Marge finally snaps him out of it by pointing out the absurdity of their beliefs. In the end, the cult's leader tries to flee with all of the followers' money in a spaceship, which is revealed to be a rickety old plane. The townspeople chase him down, and he crashes into a tree, exposing the scam. The townsfolk return to their normal lives, and the Simpsons are reunited, free from the cult's influence.