@VLAZ About Defender of the Unicorn.
Last year @YaakovEllis added a game to the Bash site - a reskin of the Google Dinosaur game. People started finding ways to cheat, so he added a bounty - the ones who found a way to cheat and reported it got the hat.
At the same time, he also had the /unicorn url on the site (a reference to previous years when urls like /dog, /chicken and so on were part of an easter egg) give out a message. "Stay Tuned". Later, the page was changed to a quiz that awarded the same hat.