What killed George "Superman" Reeves? Maybe it was eating too many boxes of Kellogg's Sugar Smacks.
Here's a one minute "in-show" commercial…a very common relic of TV shows of the past. The cast of the program would often appear in the final commercial spot…or in one occasion that you've seen, the star's relatives would do it. That commercial I linked to last week of Harpo and Chico Marx was an in-show spot done for brother Groucho's You Bet Your Life.
The thing to watch here: John Hamilton, who played Perry White, always had a lot of trouble remembering his lines. It was excusable in a way since these Superman shows were shot so rapidly and out of sequence. They'd set up for the afternoon in Perry White's office and do scenes for a half-dozen different episodes, one right after another. (This is why Clark, Perry, Lois and Jimmy almost always wore the same clothes from week to week…the same reason Dean Martin always wore a tux on his later variety show. When you shoot segments for different weeks at the same time, it's easier to not have the performers need to change wardrobe.)
Anyway, in many episodes, the director would have Hamilton seated at his desk and they'd put the script right in front of him. You can often see him glancing down to check on his next line. If you look carefully, you can see him doing it in this commercial.