Critics referred to Gene Roddenberry's Star Trek derisively as "Wagon Train in space" because of the various guest stars appearing aboard the Enterprise from week to week. After seeing Wagon Train itself, which signed off a full year before Trek launched, it's easy to understand why.
Wagon Train lasted 8 seasons between two networks, NBC (1957-62) and ABC (1962-5). For much of its run, it was a 1 hour show, but experimented with a 90 minute format for a time as well, which might've asked a little too much of viewers.
Each episode focused on one particular character, usually played by the guest star du jour. Comedian Lou Costello, in one of his last roles, appeared in a season 2 episode, for example. There are recurring, consistent themes, usually involving mistrust, which is certainly evident in "The Doctor Denker Story", from season 5, and starring Theodore Bikel in the title role.
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Currently, the Train airs Saturday afternoons on Me-TV. Not sure who else might have the rights.