Half-Life Easter Egg - Caffeine Rush

After the initial accident during your escape from Black Mesa, you'll eventually pass through the office area and vents, etc. You'll go through a large open room with plenty of headcrabs (at least 6) and a "converted" scientist with the only forward exit blocked by boards that you'll have to destroy followed by a dark hallway that turns right.

When you do so and proceed down the hallway you'll come to a scene in which two converts are feasting on a corpse - kill them then look around. You should see an espresso machine - on that machine is a VALVE logo. It turns out there's simply nothing these people can't do.

Perhaps the rush is why G-Man's eyes are so buggy looking. He looks like a cigarette and coffee man to me (pale skins, sunken eyes) haha.