Been watching the Francis The Talking Mule movies from the '50's lately, and was tickled pink to spot a very young Leonard Nimoy in a bit part. Along with a young David Janssen and James Best. That's right, The Fugitive, Sheriff Rosco P. Coltrane and Spock all in the same movie!
http://www.youtube.com/watch?v=jfv82vqG8Bk
The only other 50's film I've seen Nimoy in is the Republic serial Zombies of the Stratosphere.
Outside The Twilight Zone and The Outer Limits, have you ever spotted a future Trek actor in other tv shows and movies?
On a related note, I was watching one of the later seasons of Mission: Impossible a while back, when Nimoy was a regular. There's an episode where he's in an apartment, and a Saurian Brandy bottle is on a table. Nimoy even glances at it! That had to be some sort of inside joke.