A surprising theme for this year’s DICE Summit 2015 has been about how a company’s employees, and not IP and bottom lines, are the most important thing in the gaming industry right now.

To help support this argument, Treyarch studio head Mark Lamia took the stage to tell the story of how the developer’s now beloved Zombies co-op mode for Call of Duty almost hit the cutting room floor.

Lamia reminisced about how the studio, their release date for World at War fast approaching, was behind in development and extremely stressed following up Infinity Ward’s record-setting Modern Warfare with a game that returned to the World War II setting.

Without his knowledge, a rogue team within Treyarch began working on a side project that featured Nazi zombies. Word quickly spread throughout the studio of this fun prototype that was being passed around and worked on during off-hours, and finally it got back to Lamia.

Initially, right then and there, Lamia thought of pulling the plug on this project due to the extreme crunch Treyarch was in. But instead, he decided to actually play the prototype and wait to pass judgment until afterwards. Luckily for all us fans of zombies, Lamia was pleasantly surprised that it was actually more fun than the co-op mode they already had in the game.

The approval from Lamia gave the development team a much-needed second wind, as he allowed them to continue to polish the mode in their spare time and stretch their creative wings a bit, rewarding them for their dedication and extra effort.

After a bit of time, Lamia himself then championed the mode to the higher ups at Activision, with the consensus indeed being that the prototype was immensely fun. But PR and marketing chimed in saying it would have been confusing and too far off brand to just promote outright. This is why World at War originally featured Zombies mode as an Easter egg reward for hardcore fans who beat the main campaign (it later became so popular it was unlocked from the beginning via a patch).

Somewhat surprisingly, the fans then that took the next steps with the mode. Writing fan fiction through message boards and forums, a story began to form around Zombies and why you had to fend off this horde of Nazi undead in a bunker. This led to Black Ops’ Zombies mode forgoing any sort of PR campaign as well, as it allowed the fans to continue to build the lore themselves, with Treyarch employees adding more special Easter eggs and callbacks in subsequent games and DLC to continue fanning the flames. Even during Lamia’s presentation, Treyarch game design director David Vonderhaar continued to play with fans via social media about what could be next for the mode.

Zombies mode now serves as Treyarch’s signature whenever it’s their turn in the development rotation of Call of Duty. And since they’re up to bat for this year’s Call of Duty, we’d be more than a little shocked if Zombies didn’t find a way to rear its head once more.