Portal: The Flash Version Easter Egg - G-man Sighting

In the first level with the blue lasers (15 or 16), there will be a window in the pillar in the middle of the level. Watch it carefully. After a couple of seconds a small person with a crew-cut, a black suit, and a briefcase with walk by te window. This is a reference to the G-man (Who looks the same) from the Half-Life games. Both games are from the Half-Life universe by Valve games