I really just wanted to use the giant videoscreen and Combine Advisor for something. You only really glimpse him for a few seconds when you're playing the game, once near the start and once near the end, as Dr. Breen talks to him. Again, he's on a video screen, which means he's hidden somewhere on the map in a little chamber in front of a camera in order to show up onscreen. Took me a while, but I found him. He moves around a little and makes some cool noises.