The Dancing Juice easter egg is a simple quest to unlock a secret song and an animation of the 4 characters from the zombie mode of "Call Of Duty : Infinite Warfare"
You just need to get the dancing and return to Area 51.
The cup of Dancing Juice can be found in the South area
You now have to interact with the button at the Area 51
The Alien Protector is an equivalent to the Civil Protector from Shadow Of Evil.
You need to collect 3 fuses and place them. Once done you'll be able to summon the Alien Protector.
In the area to the left of the nuke teleporter
In the South area, on a barrel
In the Northern East area, on a barrel
You can now place the 3 fuses in the subway area, just before the stairs.
Once done you can interact with those devices to summon the Alien Protector
You can collect 3 "ingredient for a free perk" to summon a Free Perk Bonus.
The Free Perk will spawn above the cliff so be sure to have the power switched on before doing thisÂ
The 3 ingredient can all be found at the center of the map