Walter Koenig had a difficult time getting roles both before and after Star Trek: The Original Series

Star Trek: The Original Series was a boost for Walter Koenig in that it resurrected his career. In an interview with IGN, the actor says before he got the job on Star Trek, he was having difficulty getting roles. So when was offered the job, he didn't understand about the impact the show would have. He was just happy to have a job.

After the series was cancelled, things got a little tougher. Koenig was already married and had a child, who was born in 1968, to support. But "the phones didn't ring." He said that had a lot to do with his looks in that he looked younger so, for a while, he was able to play teenagers so a teacher wouldn't be required on set. That was a big draw for directors, and he was able to book a lot of guest-starring roles, but by the time he reached thirty, he couldn't play a teenager any longer so the roles dried up.

By the time he got the part on Star Trek, he was already thirty and playing a young character, and when there was talk of the series being resurrected, producers thought there was no way he could still play younger as he was already eleven years older than the character was supposed to be. So he wasn't contacted for the first attempt.

"“The first shot was a panning shot of the bridge, and everybody at their stations, and I had not yet accepted the idea that we were really making this film. The second shot was Captain Kirk steps out of the lift [and] Uhura, Sulu, and Chekov run up to him. And as they were lighting that, and we were standing there waiting to shoot it with Bill there and Nichelle [Nichols] and George [Takei] and I, I said, ‘Holy cow, we're making this movie. We are really making this movie.’ And that's when I started believing.”"

- Walter Koenig

Then he got a call for the second time Star Trek was supposed to go forward, but that got put on the shelf as well, and Koenig didn't think it was ever going to happen. It wasn't until he was on the set of Star Trek: The Motion Picture, and he and Nichelle Nicols and George Takei were waiting to shoot the scene with William Shatner that he finally realized they were realling making the movie. And that's when he says he started to believe.