Very likely the ultimate holodeck episode, which fans can otherwise sometimes dread, this is the introduction of the most neurotic Starfleet officer ever, Reginald Barclay.
Barclay would go on to make a significant franchise impact even after his infrequent recurring appearances in Next Generation; aside from being one of the few minor characters from this series to have an appearance in the resulting movies (First Contact), he transitioned into perhaps a more important recurring status in Voyager as one of the most significant crossover characters in franchise history. Not too bad for someone who could easily have been a gimmick in an episode that might otherwise have been remembered only for its unusual look at the main characters.
"Hollow Pursuits" is so clever, it accomplishes those things easily, and adds an infinite amount of depth to life in the Star Trek future, addressing a form of addiction and social awkwardness that might never have been considered before and might after all have been years ahead of its time (for instance, the advent of the Internet was still years away, but this whole episode might be said to be all about it).
Barclay is depicted as a pathetic figure most of the regular characters actually make fun of behind his back (with the nickname "Broccoli;" it's behavior you would hardly have expected from them otherwise), whose retreat into fantasy is later echoed by The Doctor's literary efforts ("Author, Author") in Voyager, where pointed caricatures of all those familiar faces who we saw mocking him are reduced to worse figures more deserving of ridicule. Again, how this is accomplished and no one despised Barclay is a testament to the episode's genius.
Even divorced from the rest of the character's legacy (which could sometimes look like it was reverting Barclay back to impulses he actually overcame), "Hollow Pursuits" is easily a classic.
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