In the chapter titled "Pittsburg", after you meet two new characters, if you check one of the rooms to the right there will be a Jak and Daxter doll sitting on the dresser, along with a Nathan Drake doll from the Uncharted series on the bed. Also, in the toy store there is a Jak and Daxter and an Uncharted board game sitting on the shelves on the walls oposite to were you entered. Finally, there are four unlockable Jak and Daxter items for Ellie to wear. A T-shirt, hoodie, backpack, and googles. All of these were previous titles made by Naughty Dog.