Aliens

"Prologue" / "Bury the Hatchet" - Frozen Alien
The frozen alien is the first easter egg the player can encounter in the game. During the very first mission, once you get in the SUV, drive off the side of the road to the right and into the frozen creek, and under the bridge you will find an alien frozen in

This particular alien will bear a strong resemblance to the encounters seen throughout the rest of the game.

Richards Majestic movie costumes
First seen during the mission "Franklin and Lamar", both characters of the same name repossess vehicles for Simeon, and eventually pass through the Richards Majestic movie studios. The player can choose to hit or avoid the actors in alien costumes, whereas avoiding them will grant the player the "We Come in Peace" objective for the mission.

Lord Zapho
Lord Zapho is the unseen alien leader mentioned throughout the game. He is first mentioned by a unique encounter in the Simeon mission "Repossesion", then is later mentioned a few times by Ron on his radio show. Also he is mentioned by the same person from the previous unique encounter in the Devin mission "Eye in the Sky"