I have only watched a couple of the animated "Star Trek" shows so far. Despite overwhelmingly positive reviews, the shows are incredibly poorly animated. Fortunately, "Yesteryear" has enough going for it that it still makes it worth seeing despite the really crappy animation.
When the episode begins, Kirk and a landing party are revisiting the same planet from the episode "City on the Edge of Forever" (the Edith Keeler episode). The fact that they are there is a bit confusing since at the end of this live action show, Kirk is very clear that he never wants to come there again--and he said something along the lines of "Let's get the hell out of here". Despite this inconsistency, the rest of the show is actually quite good and it goes places the old show probably couldn't go.
After going on a brief journey through the time portal, the party returns and no one recognizes Spock! How could this be?! Well, it turned out that Spock died when he was 11--or at least that will be the case unless Spock uses the portal and goes back to prevent his own death.
This episode is nice because you get to hear Mark Lenard as Surak-- and there are several nods to another episodes--including "Journey to Babel". His wife, however, is not voiced by Jane Wyatt but Majel Barrett. Overall, this show is definitely oriented towards kids but the show had some nice lessons, some nice nods to previous shows and fits pretty nicely into the Trek canon. I would give this one a higher score had the animators not been lemurs!! Looks like crap but is worth seeing.