Close Encounters of the Nerd Kind
Game: Metal Gear Solid 4: Sons of the Patriots
When you're tracking Naomi in Act 2, follow the straight path when you find her handkerchief on the ground (no, you can't pick it up and sniff it—yes, we tried). You should have crossed a river. There'll be one crouching soldier; put him down. Keep going left, and you'll find an alien crop circle.
You'll suddenly hear Colonel Campbell start to recount his tales of abduction, blah blah blah. After listening to him blather, you'll get 1000 Drebin points.