I don't think it is stand operating procedure to have two actors star together in two episodes that are four episodes apart is it? Paul Tripp and Joan Staley starred in the "The Case of the Double-Entry Mind" and the "The Case of the Lonely Eloper". In a chronological list of episodes I saw, they are only four apart. I wonder why they did that, were they hard up to fill the roles?
shareThis isn't unheard of. John Anderson, a popular character actor, appeared back-to-back (or perhaps just two episodes apart) on The Rifleman. In one episode he was unshaven.
Episodes aren't necessarily broadcast in the order they were filmed. It's possible they were the first choices for these roles, but there weren't enough completed episodes to create a sufficiently wide gap. (This is speculation, of course.)
I can see maybe one actor doing consecutive episodes, but I think two actors in two different episodes less than a month apart, makes the casting director look less than professional.
shareHere's another example from nearly a decade later. In the season 1 Star Trek episode "Balance of Terror", actress Barbara Baldavin plays Angela, a crew member engaged to be married whose fiancée is killed during the ensuing battle. One week later she appears as the same character on "Shore Leave" where she's apparently developed amnesia (shock? PTSD?) about the death of her fiancée just a week earlier and is hitting on another crewman in the landing party.
shareIt happened a few times. Two of my favorite coincidental castings are Whitney Blake as the defendant twice in the first season and Joan Camden in the last case of the first season and the first case of the second season. Talk about timing!