No main quest
Verrückt has no main Easter egg in any of its versions. What it has is a song, a radio added by Black Ops, and a building full of sounds: voices, screams and crying set off by the player or by simply walking past.

The secrets of Verrückt in Black Ops: no main quest, but the Lullaby for a Dead Man toilet song step by step, the dentist chair and the crying oven of the starting rooms, the radio added by Black Ops, the Lost numbers, the voices and the writings on the asylum walls.
Verrückt has no main Easter egg in any of its versions. What it has is a song, a radio added by Black Ops, and a building full of sounds: voices, screams and crying set off by the player or by simply walking past.
The song of the map, by Kevin Sherwood, sung by Elena Siegman. It is hidden in the bathroom of the left upstairs area, on the German side, just before the Power Room.
The song starts after the third flush. The game plays it as a sound effect rather than as music, so it is much quieter than the songs of later maps. It is out of reach in a First Room game.
Two secrets can be found without opening a door, one in each First Room.

American side, near Quick Revive. Crouch next to the open cremation oven and a baby, a woman or a man can be heard crying, one at a time. It is easiest to hear in the first rounds, with few zombies around.
Juggernog side. Crouch next to the small wheel on the side of the chair and press the use button: a drill starts and a man screams.
The radios of the World at War version cannot be used. The Black Ops version makes one of them work: it sits on a desk, seen through a window of the balcony on the American side. Shoot it and it plays music from the Black Ops campaign, like the radio of Nacht der Untoten.
In the Power Room, a voice on the radio reads “4, 8, 15, 16, 23, 42”, the numbers of the series Lost. Crouching by the electrical equipment helps.
Open the door to the left of the Power Room and a boy can be heard sobbing quietly.
A man screams in the room with the Trench Gun, another shouts in the small room with the wheelchairs and the Thompson, and screams come from the first room past the American side before it is opened.
At the door that cannot be opened, next to the kitchen door in the Speed Cola hallway. Best heard with no zombie around.
Turn the power on and run to a balcony to hear a distorted waltz, “Valse” by Stephan Diez, from the speakers outside.
Above the stairs, “Wish too often, and your wishing well will run”, about the teddy bear of the Mystery Box.
“19382406 9:21” in blood, in the kitchen and the room next to Speed Cola: June 24, 1938, the day a meteor exploded over Chicora, Pennsylvania, and Jeremiah 9:21, “For death is come up into our windows”.
In the room covered in writing, the symbols read “Living dead” and “OHM 935”.
At the end of the American balcony, “Unattended children will be immediately sold to the circus”, in German.
On the left balcony, before Double Tap and next to a Box spot, a mannequin stabbed with knives, “1942” written on it.
Under the fountain of the courtyard, out of reach without the noclip command, sits a mounted MG42 on a black block. It was meant to be an automatic turret, cut before release; the turret came back in Kino der Toten. Its script is still in the files of the World at War and Black Ops versions.