“All Our Yesterdays” had a special-ness according to Mariette Hartley
Mariette Hartley had the enviable role of Zarabeth in the unforgettable episode “All Our Yesterdays” in season three of Star Trek: The Original Series. In the episode, Spock and Bones are sent back to the ice age where they meet Zarabeth, and Spock begins to revert to the days of his ancestors. He also starts to display emotion and falls in love with Zarabeth, one of the many reasons why this episode is often called one of the essential episodes of Star Trek.
Hartley told Startrek.com that she loved the script as well as the idea that “this strange man (Spock) was finally going to be schtupped and I was going to be the one to do it, and that I was going to be the one to teach him how to not be a vegetarian. So I loved the idea.” She went on to say that she sensed the episode was going to be special, that whether it was the script, the costume, or the makeup, there was a “special-ness” to the episode.
Mariette Hartley wasn’t wrong about how special the episode was
And she wasn’t wrong about how special the episode turned out to be as it had several “onlys” for Star Trek. This is the only episode in which only three members of the crew are seen (Spock, Kirk, and Bones) as well as the only episode where none of the action happens aboard the Enterprise. The episode also puts physiological limitations on time travel, meaning someone had to prepare for the era they were going to or they would die. And then there were the mental changes made to Spock when he traveled in the past, and this is the only episode in which these changes are covered.
But more importantly, this is the only episode where Spock reveals his true feelings about Bones’ comments about his Vulcan anatomy which would have had a bigger impact if this episode had aired in an earlier season. It would have been interesting to see if having this information would’ve changed the way Bones interacted with Spock. Knowing how Bones was written, probably not.
Hartley summed up her time filming this episode in three short sentences that we can all understand.
"At the time, I was in heaven. It was Leonard and DeForest Kelley. It can’t get much better than that."