Lost In Space - Quick Hair Brush
In the episode, "Kidnaped In Space" in the third season, towards the end of the episode Will is running away from the aliens and finds the robot. While he is talking to him you see a close-up of Will talking. You notice his hair is brushed straight. When John and Don show up you get another close-up of Will talking but this time his hair is brushed differently.
T.V, the video