I watched the episode tonight where Fred is hooked on TV and gets hypnotized to break his TV addiction. In this episode, Fred's hair is really white, and he has an Abe Lincoln beard. Anybody else notice this?

Yeah. I particularly dont care for most of year 4 and year 5.

Yeah, I noticed this. That episode was the 7th episode filmed during the 5th season but aired as the 17th. It was filmed right after Bank on This and right before The Sanford Arms. In those episodes, his hair seems normal. Go figure. Perhaps he was in a play or something.