Since "Star Trek" (1966) was only a pilot they could keep you under option for six months and change your character or even worse drop you from the series. You had no guarantees that they would sign you for the series. I thought that doing the movie (The Russians Are Coming the Russians Are Coming (1966)) would be more exciting and a great thing to do. That was a choice I had to make and you can't look back.
I was offered a role in The Russians Are Coming the Russians Are Coming (1966). They told me you either had to do the film or the ("Star Trek" (1966)) series. I chose the film, but had I known that "Star Trek" would become such a phenomena, I probably would have opted for the series.
The quotes are from the book Drive in Dream Girls
(click link to read Google Books excerpts). It has interviews with both Dromm and Laurel Goodwin. Dromm also denies any hanky panky with Roddenberry.