I agree that TNG "Tapestry" is a really great Q episode.
I like DS9 "The Changing Face of Evil," too. So many turning points for characters, all in one episode.
TOS "Obsession" isn't my favorite TOS episode, but I admire the show continuing to speak to contemporary issues in a science fiction setting. Teaching perspectives without seeming to do so.
VOY "Blood Fever" is an episode. I do love the end, when what turned out to be a teaser for future VOY episodes is revealed.
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