If you are a Walter Koenig fan like I am, you may enjoy seeing him in two episodes of "The Starlost".
I had seen one episode of this show when I was around 7 years old in 1973 or 1974, then it completely vanished. That one episode had a huge impact on me, and for years I tried to find anyone who had seen it, or knew it's name, or anything at all about it. It was not until a Star Trek convention in the early 90's that I finally did find something. It was a few black and white stills from the show at a dealers table. I finally had a clue, and at long last conformation that I did not just imagine that the show even existed. Koenig guest stared on two episodes. It's interesting that he is using a very Chekov sounding accent. I wonder if that was his choice or the producers or directors requested it.
This was grass roots classic weekly science fiction drama at it cheesiest. This show is the vital missing link between "Star Trek" and "Space 1999", and it had some of science fiction's biggest names attached to it. Amongst them are Douglas Trumbull and Harlan Ellison (who had jumped ship early in filming, and demanded his name be changed in the shows credits)

The Starlost 110 - The Alien Oro

The Starlost 113 - The Return of Oro