George Reeves (Clark Kent / Superman) was the only actor to appear in all 104 episodes of the series.
After George Reeves' death, producers considered continuing the series with Jimmy Olsen becoming the main character and including stock footage of Reeves as Superman. Jack Larson, however, rejected the idea.
In the early episodes, George Reeves wore glasses without lenses in them when he played Clark Kent. As he got older Reeves eventually needed a real prescription for eyeglasses, so he began wearing his own glasses, as can be seen in many later episodes when you can see the stage lights being reflected off the lenses.
John Hamilton, who played Perry White, had trouble remembering his lines. The solution was to film him sitting at his desk, with the desk littered with papers--including the script--so he could glance down to be prompted for his next line.
When the series was filmed in black and white during its first two seasons, George Reeves wore a brown for red, gray for blue and white for yellow costume. When the show began filming in color in 1954, he switched to the trademark red and blue suit.