The Invisible Pink Unicorn (blessed be her holy hooves) is a fictional female deity in the form of a unicorn. The goddess was invented at the usenet discussion group alt.atheism as an alternative to other parody deities like Church of the SubGenius "J.R. Bob Dobbs" or Eris of the Discordianism. Quoting from the alt.atheism FAQ:
Like most Goddesses, she's invisible and highly unlikely to exist. However, there is much argument as to her exact colour, her shape and size, and other properties of her nonexistence. She burns with anger against theists, and allegedly grinds them beneath her holy hooves.
The "believers" famous sayings about faith in the invisible pink unicorn is that, like other religions, it is founded in science and faith. Science - that states that she must be invisible, since we cannot see her. Faith - because we know in our heart that the invisible pink unicorn exists. This is of course a parody of the theological reasoning of other religions