Step 1: Turn on the power

There is a generator in the middle of the map with 3 red lights on it. Your objective is to make all of them green. For this you have to turn 3 gas valves around the map for about 6 seconds each. The first one is located right behind the Geistschild machine in the village square area, the second one is also in this area to the left of the bunker door you are trying to open. For the third and final one, you have to open the door towards the pub. You can simply look for the power cables connecting the generator and the gas valves on the floor. Just follow them to all the respective valves.

Now that the generator is working again, activate the flamethrower trap in the middle of the town square. This will blow up the wooden lid covering the entrance to the sewer area. Once you are down there, there is only one path you can follow and you should see the actual power generator for the map on the left side next to the exit.


Step 2: Rerouteing the power in the bunker

Once you are in the bunker, you have to buy the doors to the morgue and the laboratory for 1500 jolts each. Next, you have to activate 2 different control panels within 30 seconds. One of them is in morgue and the other one in the laboratory. The morgue one is just down the set of stairs on the right (when entering the area), the laboratory one is on the second floor, above the Schildblitz machine.

Now that the power has been rerouted, you can buy the door in the middle of command room to the salt mine tunnels.

Step 3: Power up the Geiskraft Transfer Device

Head down the mine until you reach a big circular room called “The Emperor’s Chamber”. This room is where most of the objectives will take place in, as it is your task to retrieve the artifact from this machine. Go up to the device and click on it. You now have to kill about 15-20 zombies to charge the machine. All zombie types will count for this.

Once it is powered up, your next objective will be to unlock the canopy that is blocking the device. To do that, simply return to the command room and turn the crank right in front of you.
Next you have to start the tesla gun assembly process. Simply walk up the stairs in the command room and press thered button right in front of you. This will conclude this step.

Step 4: Assemble the Tesla Gun
Next up is the assembly of the tesla gun. To get the 2 missing parts for the tesla gun, you’ll have to escort the Geistkraft Device into the laboratory first. There will be a red area around the device and you’ll have to kill zombies within that area to make it move. Once you’ve reached the end of the escort, the device will stop and power up a generator. Simply wait about 45-60 seconds for the generator to finish. You can now pick up the Tesla Gun barrel.

After the device has moved back to the command room on its own, you’ll have to escort it again by killing zombies in the red area, but this time it’ll head over to the morgue. Once it’s here, you have to wait 45-60 seconds again for the giant blender to finish. Once you’ve picked up the Tesla Gun core, head back to the command room and place both parts in the weapon forge (be careful though as a powerful Brenner zombie will spawn in first. Make sure to get a somewhat decent wall weapon for this part). You can now pick up the Tesla Gun, which will also unlock you the “Lightning Handler” trophy.

Step 5: Power up the Right Hand of God

Head over to the Emperor’s Chamber again and click on the right hand of god (the machine to the left when you enter the room). Once this is done, go back up to the command room and activate the big control panel behind the weapons forge. Your objective now is to activate the smaller fuse boxes 1 to 4 in sequence and to change to color of each display to the one you saw on the control panel. The 3 colors are Rot (red), Grün (green) and Blau (blue). You will have around 45 seconds to activate all 4 boxes, so you’ll have to quickly memorize the 4 color sequence, change the first display to the respective color and then make your way over to boxes 2-4. Here are all the locations:

Right next to the main panel
After going through the morgue and the going through the door leading to the sewers, this one will be in front of the Pack a Punch machine room at the crossroads.
Next to the door leading out of the Pack a Punch room to the harbor.
Next to the door leading to the tower from the pub.
Your next objective will be to head over to the tower and to activate and defend the central lightning rod. This is fairly simple and shouldn’t be too much of a problem if you use your special ability. Once this defence is done, you’ll have to activate and defend the 2 smaller lightning rods o the left and right. This can be a bit tricky solo, but should be fairly easy with a 2-4 man party. Just keep checking both rods frequently and kill the zombies as fast as you can. Be careful as another Brenner will spawn in once this step has been completed.

Step 6: Repair the Left Hand of God

After clicking on the Right Hand of God a zeppelin will spawn outside, flying in circles over the town. You have to shoot one of the 4 orange lights on the bottom of the zeppelin until a “Überschnalle” (battery) is being dropped by the ship. For this you should focus on one of the 4 lights and damage it until it’s red and eventually drops the Überschnalle. Run over to the location it was dropped to ensure that the ship can’t steal it back (which would force you to damage the zeppelin again).

Now you have to get kills near the Überschnalle to charge it up. Once it’s fully charged, simply take it down to the Emporer’s Chamber and place it in the Left Hand of God. You might have to use your camouflage ability to carry it down there or drop it multiple times, as zombies will be hitting you a lot.

The game wants you to repeat this step 2 more times. If the objective tells you to survive until the zeppelin returns, you have to end your current round or else the ship won’t spawn in. Once you’ve placed down the third and final Überschnalle, this step is done and the Hand of God now works.

Step 7: Calibrate the Voice of God

The voice of god is the machine between the Left and Right Hand of God. To calibrate it, you have to change the 4 numbers below the raven symbols on the side of the machine to their correct number. To find out the correct number for each raven, you’ll have to scan 4 portraits around the map, using a Brenner head. By now you should have already killed 2 Brenners if not even 3. Simply go back to a spot where you killed one and pick up their head. You can also just click the touchpad button to highlight the heads. To scan a portrait you simply press right mouse button (aim down sights). You’ll see a roman numeral next to the raven. The numbers go from 1-5.

The 4 portrait locations are:

Moonraven (has a moon above his head and his facing forward): This one is on the lowest floor in the morgue, on the opposite side of the sewer door.
Stormraven (facing the right): Inside the pub on the second floor.
Deathraven (facing forward): Inside the Pack a Punch room.
Bloodraven (facing the left): Outside of the church, near the M1928 wallbuy.
Now that you’ve figured out the 4 numbers you need, put them into the Voice of God machine and activate it.


“a zeppelin will spawn outside, flying in circles over the town. You have to shoot one of the 4 orange lights on the bottom of the zeppelin until a “Überschnalle” (battery)

Step 8: Defeat the Panzermörder (Klaus)

A red electric bubble will now appear above the Geistkraft Transfer Device in the Emperor’s Chamber. You have to shoot it with the Tesla Gun in order to make it open up. You can now see the sword hilt sticking out of it. Pick it up to start the Panzermörder (Klaus) boss fight.

The fight itself consists of 2 steps that you have to repeat 3 times. The steps are:

Step 8.1: Get a Überschnalle from the Zeppelin

This is exactly like step 6, so I’ll copy it again here.

“a zeppelin will spawn outside, flying in circles over the town. You have to shoot one of the 4 orange lights on the bottom of the zeppelin until a “Überschnalle” (battery) is being dropped by the ship. For this you should focus on one of the 4 lights and damage it until it’s red and eventually drops the Überschnalle. Run over to the location it was dropped to ensure that the ship can’t steal it back (which would force you to damage the zeppelin again). Now you have to get kills near the Überschnalle to charge it up.”

Step 8.2: Attach the Überschnalle to the Panzermörder (Klaus)

Shoot Klaus until you’ve stunned him (the game will tell you when you’ve successfully done that) and attach the Überschnalle to him. Once you’ve done this for the third time, the boss fight will be over.

As you know Pack-A-Punch from previous zombies, this is a tool which upgrades your weapons and it costs 5000 points and also you can get ammo there into these weapons for 4000 points.

I'll show you how to get Pack-A-Punch step by step.

Step 1: Turn on the Power

There is a generator in the middle of the map with 3 red lights on it. Your objective is to make all of them green. For this you have to turn 3 gas valves around the map for about 6 seconds each. The first one is located right behind the Geistschild machine in the village square area, the second one is also in this area to the left of the bunker door you are trying to open. For the third and final one, you have to open the door towards the pub. You can simply look for the power cables connecting the generator and the gas valves on the floor. Just follow them to all the respective valves.

After that in the middle of the area you can press a button. Huge flames come through the floor and a few fire zombies will attack. Kill the fire zombies, drop down the hole that was blasted open by the flames and press the generator button down there.

Step 2: Power switches in Bunker

Open the Bunker door for 1250 Points. Inside, open the next two doors for 1500 Points each. There are only 2 doors you can open inside, the third door says it doesn’t have sufficient power. Use the crank in the laboratory room of the bunker. Then in the areas through each of the doors is a power switch. You must activate one power switch and VERY QUICKLY run to the other power switch . If done correctly you have now fully activated the power on all of the map.

Step 3: Hit the button near the Pack-A-Punch cage
From the bunker, head to the bloody basement. Or you can simply jump down through the big hole in the second area. It’s flooded with blood and there’s a cage in the middle. Here you can press a button that will lift the cage a little. Pressing this button opens up 3 Disposal Tubes around the map.

Step 4: Jump through all 3 Disposal Tubes

Each tube cost 250 points and its interactive. One is in the bunker, laboratory area where you use the crank. The second is also inside the bunker, in front of the Schildblitz perk. The third is at the tower where you have to defend the lightning rod for the easter egg. Each tube brings you back to the Pack-a-Punch Room. After exiting each tube you’ll be standing in front a button. (they are all in the Pack-a-Punch room but only accessible after using each tube).

That’s it!
Once you’ve gone through all 3 tubes and pressed their buttons the Pack-a-Punch Machine is unlocked!

In progress

The zombies mode in CoD WW2 features two easter egg quests with one being dubbed “Casual” and the other the more challenging “Hardcore” mode. For the casual mode your goal is to find an artifact that grants you the “Fireworks” achievement, you can check it out in the first tab, and for the hardcore one check out this one step-by-step breakdown below.

So first things first, before attempting the Hardcore easter egg you have to make sure you and every member of your team have upgraded your Tesla Gun with the four elemental variants which can be done during a run of the causal easter egg. To get the gun itself check out the guide about upgrading tesla gun, and the four variants available for upgrade and what they do are:

Midnight – shoots a straight line of murderous light that can cut through enemies easily.
Reaper – freezes a targeted zombie, and then explodes its body after a few seconds and damages any nearby enemies.
Bloodthirst – shoots a bolt of red lightning stunning nearby zombies, causing them to explode after a few seconds.
Hurricane – shoots a ball of electric pink light that expands and kills those in its radius.
We also have a step-by-step guide in getting every single one of the variants, so make sure to go back and get those before going forward with the Hardcore easter egg path.


Bring Power To The Pub

Go to to the Riverside area of the map, face the outer wall and look for a rooster-shaped weathervane. Interact with it and it will point you to a glowing button. Shoot it. The water wheel by the docks will start and you need to shoot its exposed wires with an upgraded Tesla. With power restored, you can interact with a record player in the pub.


Enigma Machine Puzzle

There are Zombie spawn windows in the Square, Riverside, Courtyard, Pub and Village Entrance. Look in these windows for Enigma Machines with colored ribbons corresponding to the tops. Note the number and color of two machines, then head back to the toy window. Use the ribbon colors and paired numbers to arrange the tops like a clock face. For example, a red bow with a number nine Enigma is solved when the red top is rotated it to the 9 o’clock position. The corresponding number for the third top is unknown, so just rotate it until a compartment opens. Players will receive a record to use in the player.


Reset Bunker Power

A Zombie head is required for this step, and players must have encountered the Zeppelin as well. Just like in the casual quest, quickly reset the Laboratory and Morgue power switches. To the right of the Salt Mine entrance, there is now a third switch that must also be activated. Shoot the exposed wires from the newly opened panel with an upgraded Tesla.


Unlocking The Safe

Take the Zombie head and bring it to the stairs that lead to the Morgue and Laboratory. There’s a gray panel on each wall next to the stairs. Shine the head there to reveal two five-digit codes. Rotate the numbers until a set of codes are highlighted in blue. Players only have 30 seconds to do all this, so have one person at each point ready to go. Take the parts that come from each of the two panels and insert them into the small stone circle behind the hilt beneath the statue. One player will get the Red Talon sword.

Charge The Player

Go to the pub and get 30-50 sword kills from the start of a new song to when it finishes. Stay close to the record player to ensure it gets charged.

Get The Player Code

Listen closely to the warped record to get a code. Wait for a long pause, then count the number of clicks between each short pause. For example, two clicks [short pause], three clicks [short pause], one click [short pause] and two clicks [short pause] reveals the code 2312.

The Second Voice

Once the Casual quest is completed up to its final step, input the code that came from the record player into the Voice Of God device between the two hands. Enter it in this order: far left (#1), center left (#2), center right (#3) and far right (#4). Hold interact to confirm the code, and shoot the chandelier with all four Tesla variants.


BOSS FIGHT
This final boss fight will play the same way as the Casual path, but will be noticeably harder.

SO GOOD LUCK

The “Midnight” Tesla variant shoots a laser beam of deadly light that cuts directly through enemies in a straight line. Create a line of zombies and blast all of them at the same time to wipe out entire groups.

How To Get The “Midnight” Tesla Variant

• Collect a Brenner Zombie boss head.

• Shine the purple light onto a statue to the left of the stairs to the Courtyard. The statue will shatter.

• Shoot the broken statue with the Tesla Gun and collect the battery.

• Place the battery in the charger in the Courtyard nearby.

• Get kills with the Courtyard trap (30~) to charge the battery.

• Complete the ‘Firework’ casual Easter egg quest step where you’ll need to protect the lightning rods at the base of the Tower.

• Take the battery and return to the lab. Place it to the left of the machine that spawned one of the Tesla Gun parts.

• Protect the battery (1-2 minutes) and collect the part from the crafting station.

• Return to the Weapon Forge in the Command room and use the part plus the Tesla Gun.

The “Reaper” Tesla Variant is even more powerful than the “Midnight” and is absolutely required for the hardcore Easter egg. This weapon freezes a zombie with sparking energy that explodes after a few seconds, killing any nearby zombies.

How To Get The “Reaper” Tesla Variant

• After collecting the Tesla Gun, make sure the doors to the Sewers (the Pack-a-Punch upgrade station area) are open.

• Lead a large zombie with the mace-arm to the Weapon Upgrade Station area of the Sewers. They will spawn in Round 7+.

• The large zombies need to hit the gray door-like compartment one the exterior wall. Just stand in place in front and take the hit to make sure the compartment opens.

• Collect the battery and place it in the charger station near the Weapon Upgrade Station.

• Activate the Saw Trap in the Sewers to charge the battery with bomber zombie souls. Only 4-6 are required.
  
• The battery will glow green when zombies are standing close enough to accept a charge.

• Complete the casual Easter egg step requiring you defend the lightning rods at the base of the tower.

• Place the battery in the slot to the right of the Tesla Gun Part spawner in the Morgue.

• Defend the battery until a part appear in the machine.

• Return to Command and insert the new part with the Tesla Gun to create the “Reaper.”

How To Get The ‘Bloodthirst’ Tesla Variant

Bloodthirst – shoots a bolt of red lightning stunning nearby zombies, causing them to explode after a few seconds.

• Use the normal Tesla Gun to shoot a flickering street lamp in the Riverside area. The lamp buzzes when you’re near — find it to the left of the path down to the docks, behind the large statue.

• Shoot the strange green sparks that appear from street lamps — follow a path from Riverside, to the Village Entrance, to the Village Square, to Command, then finally the Morgue.

• Collect the battery on the ground in the back room of the Morgue, down the steps. It will appear if you shoot every sparking green light.

• Place the battery in the charger just to the left of the battery spawn point, next to a metal gate with yellow light streaming through.

• Kill Pest Zombies to charge the battery. It will take 30-50 Pest Zombie souls to fully charge the battery.

• Continue to follow the casual Easter egg steps until you complete the lightning rod defense at the Tower.

• Place the charged battery in the slot to the left of the Morgue Tesla Gun part spawner.

• Defend the battery from waves of zombies until the part spawns.

• Insert the part into the Weapon Forge on the upper floor of the Command Room to unlock the Bloodthirst variant.

How To Get The ‘Hurricane’ Tesla Variant

Hurricane – shoots a ball of electric pink light that expands and kills those in its radius.
We also have a step-by-step guide in getting every single one of the variants, so make sure to go back and get those before going forward with the Hardcore easter egg path.

• Lead a Bomber zombie to the Lab and let it explode over a gray metal panel.

• The panel is on the landing up the steps to the left of the Tesla Gun part spawning machine.

• Take the battery inside and place it in the charger located in the electricity trap hallway.

• Wait until two Wustling (large charger zombies) spawn in a wave. Kill two Wustling zombies at the same time with the Lab electricity trap to charge the battery.

You’ll need to do this twice — for a total of 4 Wustling zombie kills using the trap only.

• Complete the lightning rod defense quest at the Tower while completing the casual Easter egg.

• Grab the battery and place it in the slot to the right of the Lab Tesla Gun part machine.

• Defend the battery from waves of zombies until the part spawns.

• Insert the part into the Weapon Forge on the upper floor of the Command Room to unlock the Hurricane variant.

IN PROGRESS

I don't know whether it is true or not, because I have not tried it on my own. But the source is : http://gameranx.com/features/id/126452/article/call-of-duty-ww2-zombies-how-to-unlock-secret-playable-characters/

B.A.T. Agent:
Kill a Treasurer Zombie.
Kill the Panzermorder, 1st Time.
Survive 25 Rounds.
Unlock the Weapon Upgrade Station — ‘Pack-a-Punch’, 1st Time.
Assemble the Tesla Gun by Wave 6.

Survivalist:Get to Round 30 without purchasing perks.
Get to Round 30 with just the starting weapon.
Get to Round 30 with only two or less Mystery Box purchases.
Get to Round 30 without turning on the power.
Get to Round 30 without going down once.

Hunter:
Obtained Zombie Hunter part A — random Treasurer Zombie drop.
Obtained Zombie Hunter part B — random Treasurer Zombie drop.
Obtained Zombie Hunter part C — random Treasurer Zombie drop.
Obtained Zombie Hunter part D — random Treasurer Zombie drop.
Obtained Zombie Hunter part E — random Treasurer Zombie drop.

Mountaineer:
Survived 20 rounds without opening doors.
Survived 25 rounds in the Prologue.
Survived 25 rounds in the Prologue without going down once.
Survived 20 rounds without opening doors or going down once in Prologue.
Survived 25 rounds without unlocking the secret room in Prologue.

B.A.T. Elite:
Saved Klaus (completed the Hardcore Easter egg) solo.
Saved Klaus (Hardcore Easter egg) by round 16.
Saved Klaus (Hardcore Easter egg) in 75 minutes or less.
Saved Klaus (Hardcore Easter egg) without going down once.
Saved Klaus (Hardocre Easter egg) without using specials, consumables or Mods.

Assassin:
Defeat the Panzermorder by Round 12.
Defeat the Panzermorder without using the Weapon Upgrade Station.
Defeat the Panzermorder without purchasing perks.
Defeat the Panzermorder without going down once.
Defeat the Panzermorder without using specials, consumables or Mods.

Those characters are the only known. Later I'll update it for the rest of them