The Undiscovered Country was billed as the farewell to the original cast, one last send-off before turning the future of the franchise over to The Next Generation. If you haven't seen it or don't remember, the teaser was a series of scenes from the Original Series as if they were projected on the surface of the Enterprise. It was a powerful and special moment seeing those scenes together in the loud appreciative audience of fellow Trekkies.
Star Trek had an enormous impact on me. I literally grew up watching these characters every week, and traveled the galaxy on adventures along with them. I watched the movies, collected starship blueprints, read articles in Starlog, and made up my own fan theories. Seeing that teaser was the highlight of the trip. I thought maybe someday it might be available on VHS to watch again. I couldn't have guessed then that "in the future" it would be available anytime on YouTube on a networked pocket computer more powerful than a Starfleet communicator.
What I find most compelling about the Original Series besides the great storytelling and action, even more so than the later series, is a vision that the future can be better. We can work together to make it so, like the crew of the Enterprise -- not in spite of our differences, but because of them.
Happy 50th to Star Trek, and to all of us who kept it alive. Live Long and Prosper.