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.

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.

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.

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.

The Predator reticle for the Reflex Sight was inspired by the Predator's laser sight from the Predator films.

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.

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.

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.

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.

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.