After the big bar fight in the beginning of the game, if you walk over to the other side of the bar instead of following Sully, you can find a newspaper that reads, "Scientists are still struggling to understand deadly fungus." This is referencing the fungal infection in the game "The Last of Us." This easter egg was planned to be removed by the development team before the game was shipped (as they were not planning to reveal the game until much later) but forgot about it and released the game with the easter egg still in.