Probably no-one. It is put forward as an argument against gods since it is just as reasonable to believe in an invisible pink unicorn as it is to believe in gods, you can't prove either one.
The Invisible Pink Unicorn is a satire on religion and gods/goddesses (and for a few people, a serious religion itself) which especially showcases the inherent contradictions of many deities - exemplified by being both pink and invisible at the same time - and the arbitrary nature of many gods.
It is magical and very few people believe in it. Unicorns have many powers such as healing, purifying water, and bringing good luck.
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The unicorns are not named, but many people refer to them as Pink and Blue.
The Well of the Unicorn has 338 pages.
The Load of Unicorn has 239 pages.
The Unicorn Series has 244 pages.
Sign of the Unicorn has 186 pages.
The Unicorn Murders has 240 pages.
The Black Unicorn has 320 pages.
Unicorn Variations by Roger Zelazny has 217 pages.
Air is invisible and has no color, taste, or odor. Many people mistakenly believe that air is primarily oxygen. Actually oxygen only composes 20% of the air we breathe. Air is full of many things we seldom think about.