What is unicorn on Stack Overflow?

Question

When I search "unicorn" on meta, it gives me about: 150 results.

When I do similar search on google, it is more then 5,500 results.

And wikipedia says this:

The unicorn is a legendary animal from European folklore that resembles a white horse with a large, pointed, spiraling horn projecting from its forehead, and sometimes a goat's beard.

It was depicted in this picture

What does unicorn mean on Stack Overflow?

Edit:
What may make the site purple with unicorns refer in this post by Joel:

If you think we should black out the site, or white out the site, or make the site purple with unicorns, take a stand, state your case, bring it up, and convince the community. We're here to serve the community and we'll back you up whatever you decide.

and this comment.

Additionally I would like to ask how all these unicorn pictures are done?
Obviously this was done by hand made but how are
https://meta.stackoverflow.com/users/137537/boltclocks-a-unicorn
https://meta.stackoverflow.com/users/42471/jared-harley
https://meta.stackoverflow.com/users/151013/the-unicorn-whisperer
https://meta.stackoverflow.com/users/131061/marcgg

avatar picture done?

Answer 1

The first April Fools day Stack Overflow experienced was graced by a third party website called Unicornify.

The Fancy and Amazing April Fools question

There may have been some minor discussion of unicorns prior to that, but more discussion involved ponies (thanks, TheTXI) than Unicorns.

It has since that time become a meme within the community - something of an inside joke. It has little specific meaning, and is instead invoked whenever someone wants to inject some amount of humor into their post or comment.

It was significantly reinforced two years later when everyone's avatars were changed to unicorns:

My God—it's full of unicorns!

It has no other meaning or special nature on Meta, it's merely a mystical animal that's occasionally used for humor.

What may Purple with unicorns refer in this post by Joel

He was saying that if the community demanded a ridiculous design for Stack Overflow (a purple color scheme decorated with unicorns) in order to fight a government regulation, then Stack Exchange would create that ridiculous design.

He was essentially saying that they would go far to enact the community's will in this matter by giving an example of a funny extreme.

Again, using unicorns as a funny inside joke and meme.

Answer 2

Unicorns are the magically weaponized form of a pony.

The Many Memes of Meta

Answer 3

A unicorn is, as noted, a mythical creature. A horse/pony with a magical horn growing from its head. It is generally seen as a "sweet, kind, gentle" yet powerful creature. The mere sight of a unicorn is supposed to be a semi-magical event, as they are quite reclusive (as are most mythical creatures, I hear)

The use of it on this site flows from the fanciful nature of the creatures. They are sometimes used to refer to things that are a bit of a fantasy, or things which may be fleeting. Often, they are used to refer to things which are really "cool", on a near-mythical level.

For instance, in discussion on my recent proposed FAQ entry about Down Voting, the reputation points I gain from that post until it is made Community Wiki were referred to as "Unicorn Points".

Answer 4

Actually, the unicorn on Stack Overflow predates the April Fools' thing and even Stack Overflow itself.

It was from a slide during the original VC funding round to get money to create Stack Overflow.

Here's the original blog post from Joel himself: http://www.joelonsoftware.com/backIssues-2010-05.html