[[quoteright:350:https://static.tvtropes.org/pmwiki/pub/images/star_trek_tas_tearjerker.jpg]]
[[caption-width-right:350: ''Franchise/StarTrek'' meets ''Film/OldYeller''.]]
* When Spock decides that his mortally wounded pet sehlat has to be put down, it's a heartbreaking moment for Amanda; and also to Adult Spock, when he comforts his dying pet.
** Also from "Yesteryear", the glimpses at Spock's childhood. The poor guy has been getting mocked and humiliated since long before what the original series shows. It gets even worse because [[WellDoneSonGuy Sarek]], rather than being annoyed at the Vulcan children for (illogically and emotionally) picking on his son, gets disappointed at Spock for not being more Vulcan. Oh, Spock, you StoicWoobie, you...
* In "Beyond the Farthest Star" the villain is an EnergyBeing that has been alone for 300 million years. After it is defeated, its despairing pleas not to be left behind once more are [[CryForTheDevil surprisingly heartrending]].
* Near the end of "How Sharper Than A Serpents Tooth", the crew manage to subdue Kukulkan. Though the victory is slightly bittersweet. Kukulkan sees the error of his ways, but decides to head off into deep space to live the rest of his long life alone.
* In "Pirates of Orion", [=McCoy=]'s reaction when it's found that the medicine needed to save Spock has been stolen by the titular Orions, and there seems to be nothing they can do. The animation's substandard quality doesn't provide for much facial expressions, but the dialogue's tones reveal the doctor's frustration and helplessness. After all, it is a physician's nightmare -- he has made the diagnosis, he knows the right prescription, and still there is no way he can save his patient, [[VitriolicBestBuds who happens to be one of his closest friends]].
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