Call of Duty: Black Ops Cold War Teases New Mission for Zombies Outbreak ✖ It looks like a hidden mission, aka the long-awaited "Easter Egg," is making its way to the Zombies Outbreak mode in Call of Duty games have included when players refer to as an Easter egg, though these are really secret missions that lead deeper into the overall lore of the Zombies story. The open-map Outbreak mode didn't include any of these big secrets when it launched, but the development teased that there would be something revealed later. It appears as though the big reveal is just around the corner.