There are a few easter eggs and references scattered throughout the game.

The first one is in Blvd. St. Michelle on the junction box by the vent. It reads Lv426, an obvious reference to the Alien franchise.

The second one is in the washroom. If you examine Collin Jameson's body with Karne, he will comment that he suffered multiple stab wounds, and is located right outside a bloody open shower. This is a reference to the movie Psycho.

The game also features literary references, such as the Pickman's Drawing that you find in Dorm 1, a reference to the H.P. Lovecraft short story Pickman's Model. In a way, the game itself is a love letter to Lovecraft's work, but set on Mars. Plenty of Shakespear refereces as well.

Hope you enjoyed, and if you notice any more, post them here.