I found the easteregg (definately)

[Adam]

Does this help?

Nevermind.. its a picture of the scientist and he has the valve logo look to him because he has a valve right behind his head from a background pipe.

 

[Chicky]

um was it nessecary to bring this thread back to life?

 

[Thadius Dean]

well for you it wasnt. but hey, i was curious.

 

[soman]

cant the easter egg be that theres one person in the game with 2 faces(2 identies or more, one being only true), and you can only spot who it is by seeing they have the same eyes? Or at some scenes a character becomes a nother character trying to misslead freeman or someone that changes eye color, not being fully human.

 

[bastard_loud]

Close, soman.

Actually, the easteregg is Gabe Newell disguised as Dr. Kleiner.
He be foolin' all joo noobs.