From DownSights: “If you’ve played Die Maschine, then you would’ve definitely completed the infamous Coffin Dance Easter Egg. Similar to that, there is a brand new version of the Coffin Dance Easter Egg in Firebase Z, called the Bunny Easter Egg or The Evil Blue Bunny Easter Egg.
Upon completing this easter egg, you will get a guaranteed free Jugger-Nog perk similar to how you got one performing the Coffin Dance easter egg, salvage, and a high tier weapon. You can also get the RAI K-84 wonder weapon if you’re lucky!”
Source: N4G PC How To Do The Bunny Easter Egg On Firebase Z (Free Jugger-Nog Perk)