Every single map has one of these easter eggs, usually triggered by interacting with three objects around the map.
Music Easter Egg
What is the name of the orb used to collect the souls of the ultimis crew in Black Ops 3?
The Summoning Key
This robotic soldier zombie can shoot it's claw at you and spray fire
Panzer Soldat
Mustang and Sally
M1911
Undead George Romero roams around on this Black Ops I map
Call of the Dead
Which map features a series of masks and hats that give different buffs?
Revelations
What is the name of the book that contains the entire stories of zombies, and guides Richtofen where he needs to be?
The Kronorium
How many Margwa variants are there?
3 - Normal, Fire, Void
Zeus Cannon
Thundergun
On this map, perks have random spawn locations and land like missiles every few rounds
Nuketown
In Origins, what item stops you from dying when the robots step on you?
Golden Helmet
This race of alien tentacle creatures first appeared in Black Ops 3
The Apothicons or The Keepers
What does the Pentagon Thief do to the player?
Steals their weapon
(Black Ops III) Dire Wolf
Dingo
Which map has a giant bell tower that you can ring by shooting it?
Der Eisendrache
What 2 perk machines have a chance of being uncovered on The Giant after using the Giant's Laser to melt the snow pile?
Stamin-Up and Deadshot Daquiri
In Moon, inserting the Vril Device into the pyramid allows which two characters to switch souls?
Richtofen and Samantha
You can tell if these enemies are ready to drop a free perk again by looking at the lights in their house
The Witches
(Black Ops II) Lamentation
Galil
This map's easter egg has the characters help out Brock and Gary, two explorers trying to uncover the secrets of Agartha
Shangri-la
Verruckt has 3 flushable toilets, what 3-digit number needs to be entered using flushes to activate a music easter egg?
9/3/5
These items, canonically collected by Richtofen between the events of Zetsubou and Gorod, act as an insurance policy so that Dr. Monty cannot erase the primis crew from existence after rebuilding the universe.
Blood Vials
Cornelius Pernell becomes this mini boss after a failed experiment with an elemental shard
The Avogadro
(Black Ops I) The Predator
Commando
This map is the only map in Black Ops III to have the Razorback SMG in the mystery box
Zetsubou no Shima