On STAR TREK, there were only three actors that were considered regular cast members. And even DeForest Kelley wasn't in "Where No Man Has Gone Before" (the first episode in production with the new cast, but not the first episode aired). All the other actors were recurring cast members and would have had different contracts. A fact that George Takei glossed over. William Shatner was actually the only star on the show (in the first season), which is why he got special privileges.
The Pike episode was the original pilot but the network didn't give that the green light. "Where No Man Has Gone Before" was the new pilot with Shatner in the lead and that's the one that got picked up.
If you count original pilots that were turned down and then recast, there would be a lot less shows to consider.
There have been many shows where an actor is a series regular yet is credited as a special guest star. On LOST IN SPACE, for example, Jonathan Harris was a special guest star in the first episode. He was supposed to leave after that, but Harris connived his way into getting the biggest part on the show.