User blog comment:Argorrath/Treyarch releases a BO2 teaser video called "Origins" for DLC 4/@comment-67.169.165.224-20130808041420/@comment-11037376-20130808053534

Or the Original 4 became slightly older, as the new four did all of that stuff, and had to go back in time to the start of the zombies, in order to save the Earth from complete disaster. When you think about it, the characters do look kind of older.