When using Tactical Insertions in Multiplayer, a set of numbers will appear on the small screen of the device. These numbers change for each map and are actually real-life geographic locations and, via Google Maps, are shown to lead to places that highly resemble the map they're displayed on. Two notable examples of this are the maps "Hijacked", which leads to a ship off of the cost of an island, and "Express", which leads to a train station in Los Angeles.
An unused camo called "Massacre" can be found in the game's files. It looks similar to the red camo from Call of Duty: Black Ops, but it's darker.
There are two scrapped multiplayer maps that can be found within the game's files. The first is Promenade, which seems to be an early version of Plaza. The other scrapped map is an early version of Standoff.
There is a label on the back of the Guardian that reads "1.21 GW". This is a reference to the Back to the Future movies, where 1.21 Gigawatts are required to activate the DeLorean time machine.
When the Mystery Box is not active in the Zombies game mode, a teddy bear will be left in its place. Every so often, the bear will move its head, as though assessing the area, and then return to its original position.
The Predator reticle for the Reflex Sight was inspired by the Predator's laser sight from the Predator films.
There was a mode cut from the game called "Hacker". The objective would have been to disable and hack neutral A.G.R.s (Autonomous Ground Robots). Points would be earned both for hacking the A.G.R.s and killing other players, with using the A.G.R.s to kill other players rewarding the most points. The only thing that remains of this game mode, however, is a cut menu icon.
In the PlayStation 3 release, placeholder text scripted as "MENU_DLC5_MAPS" can be found in the game's code, hinting that Treyarch may have considered releasing 5 DLCs instead of the final 4.
In patch 1.12, the Ray Gun Mark II was unintentionally added to every zombie map before the DLC Vengeance came out for Xbox 360. It was later removed with a hotfix a few weeks later.
Near the end of the Nuketown Zombies trailer, one of the CDC characters can be heard talking, but in the actual map none of the 4 characters have any quotes.
Upon entering 115 into the number pad in Mob of the Dead, the player will hear "Not this time" or "Maybe next time" and the number will change to 666 referencing the Bible and the number of the beast.
Inside the trailer in the DLC multplayer map Studio, multiple weapon props can be found. Dual Ray Guns, Sliquifiers and Vektor K10s as well as an unknown weapon.
There is an Atari hidden in Nuketown 2025 with 4 playable games. To accomplish this, you have to shoot the heads off all mannequins in under 2 minutes. Also, while playing, your character's hands will pixel-ate.
In Nuketown 2025 there are books that read "Edward Richtofen", a character from the original Black Ops.
Unlocking all gold camo's in a weapons class (Such as Assault Rifles) will result in Diamond camo being unlocked for that class.
Throwing a monkey bomb in zombie mode into a lava pool or outside the map will result in the monkey bomb not functioning and a demonic laugh being heard.
On the zombies map Green Run the original zombies map 'Nach Der Untoten' can be found in the cornfield. Only the spawn room can be entered however.
The population counter in Nuketown Zombies counts down for every zombie killed. After every 100 zombies killed, the clock on the map will turn 1 hour. When the population is 11 and the clock is at 5, a Fire Sale power up is present in the garden shed with a power-up in it. Furthermore, every time the clock changes the power-up changes too.
If the player makes it to round 25 on Nuketown Zombies the Zombies eyes will turn blue which represents the change in control over the zombies. Also the demonic announcer changes to Richtofen.
While playing on Nuketown Zombies, a speaker next to a TV in one of the houses will play Richtofen's voice (from the original Black Ops Zombies) saying various phrases from the Moon easter egg portraying how Nuketown Zombies and Moon occur at the same time.
While playing on Nuketown Zombies, if the players shoot the heads off all the mannequins, an 8-bit version of Pareidolia or Coming Home will play, a reference to the first Black Ops.
While playing on the Nuketown Zombies map the bus horn from Tranzit can be heard in the background.
On many of the multiplayer maps white boards can be found with posted notes that state "Zombies are coming" Some of the maps these boards are found on are Cargo, Standoff and Turbine.
In the Nuketown Zombies map a fallout shelter is found in the backyard of one of the houses, knifing this fallout shelter causes Marlton from the Green Run map to be heard inside.
Thor's Hammer can be found in the campaign level Celerium. After the parachute sequence a path on the left leads to a dark cave where the legendary hammer awaits. It is recommended to use a millimeter scanner to see the hammer more clearly.
Through the use of theatre mode the player can explore the entire Green Run map without the fog. This can only be done by pausing a replay video of Green Run when the power is turned on and exiting the building through free view.
If you shoot Mason in the Foot instead of in the head he will appear in the final scene before the credits. Also, it will unlock a secret ending at the end of the credits where Woods, Menendez and others preform a rock concert.
In Zombie mode, if you go to the diner and look at the big sign just outside of the diner, it will read "NOW DIE".