"....geez, I feel like I'm Don Quixote"

Here's a little TV trivia.

There was a pair of actors who once starred on a sci-fi show together. One went on to portray a starship captain and the other a humanoid robot clone intent on destroying the human race.

Who were these actors and what show did they star in together?

Hint: Its first episode aired 20 years ago.

Once you think you have the answer, check the comments - I'll place the answer in the comments.