Lisa abandons her Christian faith (after the local church sells ad space inside of it to cover the damages done by Homer and Bart's toy rocket) and opts for a new one that still allows her to be close to God, Buddhism. When words gets around, Marge tries to win her back to Christianity, but Lisa refuses.

!!Tropes of this episode:
* {{Bowdlerization}}, WordOfGod, and WhatCouldHaveBeen: Originally, there was supposed to be a scene where an Arab man named Hassan Jay Salam is arrested for shooting the rocket into the church because the rocket has his initials on it (which are actually Homer's initials), but, because of the 9/11 attacks and fear of backlash from Arab viewers, the producers had the scene cut. The DVD commentary talks about the missing scene.
* CallBack: Benjamin, Doug and Gary from the episode "Homer Goes to College" have a cameo.
* CrisisOfFaith: Plot of the episode.
* JerkWithAHeartOfGold: Kearney, a known bully and petty thug, is right to point out what has to be done about the church, making it a priority. Burns also fits this trope; after all he did help rebuild the church, even if the advertisements inside were in bad taste.
* KidHasAPoint: Lisa does explains to Bart she's not going for a new way to worship just because it's sounds cool, she rather find one that brings her peace while reminding God that she still respects Him.
* MoralDissonance: At the start of the episode Lisa leaves her Christian faith because she feels her local church has become too commercialized. She then become a Buddhist, but is confronted by a dilemma because her parents try to lure her back in by celebrating Christmas (in the incorrect notion that this feast is exclusively a Christian holiday: the feast itself was already celebrated by pagans centuries before Christianity claimed it). Lisa likes celebrating Christmas, but at the same time she wants to stick to her Buddhist beliefs. Then Richard Gere informs her that while Buddhism is about one finding inner peace, it is also about respecting the diversity of other religions based on love and compassion - thus, Lisa is free to celebrate any holiday with her family including Christmas. So... when you think about it: Lisa now more or less joins Christianity again for the same reason she originally abandoned it: she just wants to have her Christmas presents and take part in a holiday celebration that has become increasingly commercialized in recent times!
** It's even worse when you remember "Homer the Heretic", which had Homer portrayed as inherently wrong for shunning the church, whereas here Lisa is portrayed as inherently right.
* OutOfCharacterMoment: Marge is very intolerant of Lisa leaving Christianity and joining Buddhism, while Homer isn't particularly bothered by it.
* PetTheDog: Even though he opts for commercialism, Mr. Burns does live up to his promise to help rebuild for the church.
* RecognitionFailure: Despite being a Buddhist Lenny astonishingly has no idea who the Dalai Lama is, nor Buddha.
* SpecialGuest: Richard Gere as himself.