For the most part, Star Trek the Animated Series isn’t really treated as canon for the original crew. But the cartoon did get a couple things into the canon, and many of them come from this episode. “Yesteryear” is largely about Spock, and of course that means it was written by D.C. Fontana. She always did write the best Spock material.
This episode also acts as a follow-up to another episode, namely “City on the Edge of Forever,” possibly the best episode of the original series. Oddly enough, this is the only time the Guardian of Time ever got a visit in any other Trek series, and, quite frankly, if this is the sort of thing that can happen when you do even basic time travel, then it makes sense that the Federation marked the whole thing off-limits.
Of course, we also get to see Spock’s childhood pet in this one. Referenced in “Journey to Babel” by Spock’s mother as a large, living teddy bear with fangs and claws, that is indeed what I Chaya is. And, as it is, I Chaya is the reason the episode itself is so memorable, but I am getting a bit ahead of myself.
Kirk, Spock, and a nameless redshirt come back from a journey through time where they witnessed the birth of an ancient civilization on behalf of some historians. But McCoy, waiting for the party, wants to know who Spock is. Sure enough, only Kirk and the nameless redshirt remember Spock exists, and the reason for it is, in this timeline, Spock died as a child, and his distraught mother Amanda died shortly after that returning to Earth when Spock’s parents subsequently split up. Sarek never remarried and threw himself into his work. And the Enterprise‘s first officer is an honorable warrior Andorian.
Apparently, Spock recalls an incident from his childhood where an adult cousin saved his life about the time of his Vulcan rite of adulthood for children. While Spock, Kirk, and the other guy were watching the birth of that civilization, McCoy and the historians were watching Vulcan from the period of Spock’s childhood, and the adult cousin was indeed an adult Spock. Since Spock wasn’t there, his younger self died. Spock, as a result, needs to go back in time, pose as a cousin, and save his own life.
That is more or less what happens, but there is a twist that’s a bit unexpected for a kid’s show: I Chaya died. Young Spock, having trouble keeping his emotions in check thanks in no small part to the fact he’s bullied by other kids for being half-human and Sarek’s own logic-based expectations, ran away from home to prove himself. I Chaya followed and attempted to protect the boy from a Vulcan predator, and while adult Spock did use the nerve pinch to stop the animal, I Chaya was infected with a poison that was killing him. Young Spock does manage to get a healer, but they don’t return in time and a decision needs to be made: euthanize I Chaya and end his suffering, or prolong the pet’s life and pain.
Young Spock chooses euthanasia.
Yeah, that happened. A big, somewhat cute-looking animal that only communicated in sad whimpers, already old and fat and apparently also Sarek’s childhood pet, died.
You better believe the network didn’t want that, but Gene Roddenberry had the final decision, and he went with euthanizing Spock’s childhood pet.
Granted, this was the incident that helped Spock crystallize his decision to follow the serene path of logic, partially using his older “cousin” as a model.
And then grown-up Spock returns to his own time. Kirk is waiting for him, and I do wonder if Kirk remembers the whole incident because no one else does. McCoy starts grousing again, but Spock makes a remark about how McCoy could have had to deal with an Andorian instead.
So, what from this episode stuck around? Well, Mark Lenard did return to voice Sarek according to Wikipedia, but the closing credits don’t list any cast members outside the regulars. The kid actors playing the young Vulcans are uniformly terrible, but that’s par for the course for a lot of animation. I don’t know who voiced Spock’s mother, so it may have just been Majel Barrett.
But some little things from this episode would be referenced again. Some of the Vulcan landmarks crop up in Star Trek Enterprise, and the idea that Spock was bullied as a child is also seen in JJ Abrams cinematic reboot. But in my mind, this episode may be the high point for the animated series.
And there are only 20 more episodes to go.