Parody Religion

Exactly What It Says On the Tin. Made-up religion (made up intentionally to not make any sense for the viewer) which exists to parody some specific existing religion, a group of religions and religious beliefs, organized religion in general, or just any kind of religious belief. Usually serves as a front on The War On Straw, unless it's a someone enacting a funny God Guise, then it's just Played for Laughs.

Often takes the form of a Cargo Cult, a God Guise, some bizarre Crystal Dragon Jesus cult, or a pastiche of a Real Life religion with Serial Numbers Filed Off.

See also Path of Inspiration, which is more or less exactly this with evil instead of funny, Corrupt Church, which is against organized religion, and Church of Happyology, which is a subtrope that parodies a very specific religion.

Note that all examples must be intentional.

See also: Anvilicious, Religion Is Wrong. Contrast Saintly Church, Religion Is Right.

Examples of Parody Religion include:

Fictional

A huge amount of those from Transmetropolitan. According to Spider, new cults pop there every hour, therefore, any religious belief does not make any sense.
That rabbit cult from Looking for Group. Subverted, because there is a good reason for worship.
Futurama has recurring Robotology, Robot Judaism and The First Amalgamated Church, as well as occasionally mentioned Oprahism, Church of Trek, et cetera.
The Monty Python's Flying Circus "Crackpot Religions" sketch.
The Last Guru by Daniel Pinkwater has the Silly Hat Order, with a side order of Blong Buddhism.
The Simpsons are members of The Western Branch of American Reform Presbylutheranism, which split from the Catholics in 1573 over the right to go to church with wet hair, which the Presbylutherans have since abolished.
In Boba Fett: Enemy Of the Empire, Boba Fett tracks the eponymous enemy to a secluded hermitage on a volcanic planet, which is home to a stereotypical crazy sect called the Ancient Order of Pessimists, who are eventually wiped out by Darth Vader's Star Destroyer immediately after the High Hermit commits heresy by embracing optimism.
- "Well, this could have ended much worse..."
In South Park, Dawkins mentions the Flying Spaghetti Monster while talking to Mrs. Garrison during a lunch in the episode Go God Go.
Ceiling Cat.
Chutengodianism in Godless starts as a joke by a few teenagers, but takes on a life of its own (complete with its own heretics and fundamentalists.) In the end, the narrator is the only one left who still follows it--he doesn't really believe in it, but he wishes he did.
Xavism in Sengoku Basara is a rather overt parody of the Catholic Church; its leader is a delusional (but well-meaning) Love Freak who believes in the power of blowing the crap out of someone to convert them, all its adherents get bizarre baptismal names, and the "commandments" are all Broken Aesop versions of Christian dogma.
The movie Bowfinger features a cult called Mindhead, which parodies Scientology.

Real Life

This trope was in full effect over 300 years ago: Tsar Peter the Great and his friends formed The All-Joking, All-Drunken Synod of Fools and Jesters that not only practiced heavy drinking and orgies, but wore church attire and used religious titles when doing so. The pious Russians were not amused - some even proclaimed the Tsar to be Antichrist.
Flying Spaghetti Monster.
Invisible Pink Unicorn as well.
Various Cthulhu cults.
The Church of Google.
Discordianism has been described as a "religion masquerading as a joke" or a "joke masquerading as a religion." Both are correct.
Church of the SubGenius.
The Jedi Census Phenomenon.
- Only in part. There are people who really truly believe in the existence of The Force and who try to emulate the Jedi in their everyday lives. Places like Jedi Sanctuary, Real Jedi Knights.... Obviously, there are also Sith, though they are less extreme than in the movies.
The Last Thursdayism claims that the Universe was actually created last Thursday, and any memories or evidence of events before that were created at the same time.
- The schism known as Next Thursdayism claims that the universe hasn't been created yet, and what we think is happening now is just false memories we'll have once it exists. Of course, some might argue that both sides are heretics: The Universe was created Last Tuesday.
Tarvuism, created by the guys behind Look Around You and just as absurd.
And many, many, many more.