As an addendum to Wise, at the time they were setting up for Trek (when they opted to go from a series continuation to anchor a new Paramount network in 1978/79 to a feature film), they had all the actors locked down, with one exception, and that was Leonard Nimoy. He was in his “I Am Not Spock” phase and simply didn’t want to return to Trek.
Instead, they were prepared to have another actor, David Gautreaux, step into the part of the new Vulcan Science Officer, Xon (with the difference being Xon was fully Vulcan and having to deal with the utterly alien humans, which would’ve made him even more “alienated” from the ship’s crew). Persis Khambatta, of course, was also slated to play Ilia in the tv series, but they held her over for the film (and killed her off). I’m not sure if Stephen Collins (as Will Decker) was to be on the series or not (adding all those folks to compensate for Nimoy’s departure made for a rather top-heavy cast).
Anyway, when Wise informed his children (whom were big Trek fans) that he was on the project, they were ecstatic. When he told them, however, that Nimoy wasn’t going to be a part of it, they were horrified. They told their dad he had to do anything and everything to get Nimoy on board with the film project. Somehow he and Roddenberry managed to persuade a very reluctant Nimoy to come back, because it just wasn’t Trek without him (Trek could likely survive with the absence of one of the lesser of the trio, McCoy, or one of the rest of the cast, Chekov (who was not on the animated series), Uhura, Sulu or Scott, but if Kirk or Spock wasn’t there, it simply wasn’t going to work).
Of course, Nimoy wanted to have Spock killed off, and got his wish, sort of, with the next film...
In a way, I’m saddened that we didn’t have a second series with Kirk & crew beginning in 1979 (which probably would’ve run at least 5-7 years), though it also would’ve meant no films, no “T.J. Hooker” for Shatner, but most of all, no Spock, as Nimoy simply would’ve refused to commit to doing a long stint again (aside from perhaps a guest appearance here or there, if that... he made only one appearance on “T.J. Hooker”).
Another tidbit on Nimoy somebody pointed out on the soap “General Hospital” message board... He played a bad guy in the early seasons of the show (circa 1963). Whether those episodes still exist is another question...
I wrote all that stuff out from memory and then I realized most of it was covered, and in more detail, on the TMP page on Wikipedia (which I actually hadn’t read in full). :-P
https://en.wikipedia.org/wiki/Star_Trek:_The_Motion_Picture
Really? Ha.
Yeah they used to tape over old shows, a lot of early TV is lost forever, they never imagined people in the future might want to see it. I know this an issue with many old "Doctor Who" episodes.