Nacht der Untoten: Easter Eggs

No main quest

Like every version of Nacht der Untoten, the Black Ops III one has no main quest. Its secrets are musical: the radio of the Help room, a radio message from Doctor Monty and, new with Zombies Chronicles, a hunt for Samantha dolls that ends with a Max Ammo and a song.

The Samantha dolls

It can be done from the first round, solo or in co-op, but it needs the Help door and the stairs open: two of the buttons are outside the starting room.

Press the four hidden buttons. Each one gives a faint click, and a thunderous sound plays once the fourth is pressed. Some of them only show their prompt after a jump or from a precise spot.
Pick up the first doll. A small Samantha doll now lies on the floor in front of the RK5, by a dead body. Interacting with it starts a music box tune.
Shoot the spinning dolls. Follow the tune: where it is loudest, a small doll spins somewhere around the bunker, most of the time outside the map. Shoot it until it disappears, then follow the next one. After five or six, a thunderous sound confirms the end of the hunt.
Go back to the first doll. It now stands up and spins. Interacting with it makes a skeleton hand drag it into the ground; a Max Ammo drops and a song starts.

Button 1, the Mystery Box stairs

Under the shelves at the bottom of the stairs near the Mystery Box. Go prone to reach it.

Button 2, the spiral staircase

On the ceiling above the spiral staircase that climbs from the starting room. Jump to reach it.

Button 3, Mule Kick

High in the corner of the wall to the left of the Mule Kick machine.

Button 4, the Argus

Upstairs, on the wall across from the Argus wall buy.

The spinning dolls appear among these spots:

in the hole in the roof to the left of Der Wunderfizz;
on a fence post outside the farthest window of the starting room;
on the pond outside the left window of the starting room;
at the end of the barrel of the tank, outside the window next to Mule Kick;
on top of a power line post, seen from the top floor;
on top of a truck outside the far right window of the starting room;
next to a power generator on the ground floor, seen through a window.

The radios

The music radio

In the Help room, to the right of the Mystery Box. Shot or knifed, it plays a song; on Black Ops III the songs come from throughout the history of Zombies, where World at War and Black Ops had their own.

Doctor Monty

A radio of the map plays a message in which Monty translates the name of the map, remembers „an old concrete building on an airfield somewhere“ and tells the Ultimis crew that they were not there at first.

The Undone song and the other secrets of the earlier versions are covered in the book of the Black Ops version: Nacht der Untoten.