In the Potomac Event Center, there are posters showing some sort of warrior with the name “Valhalla” at the top, indicating the warrior is either a Viking or otherwise connected to Norse mythology. The warrior is also holding an orb that appears to be an Apple of Eden from the Assassin’s Creed series, suggesting this is a hint for a Viking-themed Assassin’s Creed game. This corroborates other rumors about the next game, especially since Ubisoft often teases upcoming games in their current games.
Down in the sewers, you can find an alligator behind some bars. It doesn’t react to you or respond if you shoot it. It is most likely a reference to the common urban legend of alligators being found in city sewers.
If you enter the sewers from West Potomac Park, you can find a red balloon visible behind some bars. The balloon appears to be a reference to Pennywise the Clown from the book and film It. Another balloon can be found in the southwestern area of the city, near graffiti that reads “Sleep.” Players have reported finding other balloons as well, which could hint at a larger Pennywise reference still waiting to be discovered as of now.
Behind the blocked door in the Space Administration HQ, you can zoom in to see past the debris to spot an alien, although you can’t interact with it in any way. This might also be a reference to the popular conspiracy theory among UFO believers that governments have secretly either captured or made deals with extraterrestrials.
In the Space Administration HQ, you can interact with four computers to open the door to a secret room, where you’ll find a stuffed turtle toy with four toy elephants on its back and then a flat Earth on top of that. This is a reference not only to flat Earth beliefs, but even more so to the comedy fantasy Discworld series by Terry Pratchett. In Discworld, the world is a flat disc carried on the backs of four elephants that ride on a giant turtle through space.
In the Theater settlement, you can unlock a game zone where you can see kids playing For Honor, another game from Ubisoft.
There is also a knight figurine in an early cutscene that could be another For Honor reference, or possibly a reference to The Settlers, which is also an Ubisoft game.
In the Taxi Graveyard, you can find an overturned taxi, a bloodstained hat, a toy snake, and a sign that reads “Clever girl,” all references to a scene in Jurassic Park.