While playing Halo3 campaign a bit this evening, I came across an Easter Egg during the mission to secure the perimeter and clear the hangar. The Covenant is attacking the base, so you have to secure the hangar for evacuation. After the first encounter, travel down the huge tunnel to the end. There is a soldier banging on the door trying to get the guy on the other side to open it. This develops into a pretty humorous exchange about whether he’s one of the enemy or not. It reminds me of the old Cheech & Chong routine "Dave’s not here!"