406 was a character in Zombieland played by Amber Heard.
406 and Columbus were neighbors in an apartment complex. Unknowingly, Columbus had a crush on her. One day a zombie, who she thought was a homeless man, attacked her and bit her. She came into Colombus' apartment looking for shelter, and eventually turned into a zombie herself. Colombus was forced to kill her with the lid of his toilet tank. This was Colombus' first encounter with a zombie.