Interestingly enough, many of the actors in these pieces, when interviewed decades after the fact, confessed that they weren’t particularly proud of their performances. The Twilight Zone had a budget, just like any other series, and often the bulk of the money per episode had to be spent on sets and special effects. There was no luxury of multiple retakes until the actor felt just right about a particular scene. A sub-par performance wasn’t a matter of concern in most episodic television of that era, but, as William Shatner later mentioned in an interview, at that time a Twilight Zone appearance was just another job – no one ever suspected that these episodes would be aired over and over (and over!) again for years to come.
There's more about your favorite episodes and about host Rod Serling. Link