Zombies Introduction:
The Zombies mode was first introduced as a bonus in World at War. The first map, "Nacht der Untoten," was a simple survival map with no story or complex objectives.
Storyline:
Zombies mode didn’t have a deep narrative yet, but it introduced the idea of Treyarch's "Nazi Zombies", with players battling zombies in a World War II bunker.
Gameplay:
It set the foundation for later titles, including the use of perk-a-colas (like Juggernog), the mystery box, and boarding up windows to prevent zombies from breaking in.