Conventions. Cosplay. Routine scholarly analysis. Fanatical extrapolation of details from within the show or work. Regularly produced extended universe media. Star Trek fans did all of that first or nearly first. Now much of this is very common for dozens of other works but Star Trek seems to have blazed the trail. Would it be fair to say it essentially created Nerd sub culture?
No.
Also,
Also no. In addition to Science Fiction fan behavior going back a long way, fan nonsense in general goes back as far as humans do. The only thing that changes about humanity, are the details of how it’s core set of values, behaviors, yearnings and so on, are expressed.
As Miller noted, the excesses of modern fandom basically start with Sherlockians. For one thing, the whole idea of a “canon” defining what is and isn’t part of a fictional universe started with them, and the 60 Holmes stories and novels are still referred to as the Canon.
I’m a little surprised we haven’t had a dedicated SF fan drop a spittle-flinging rant about conflating Star Trek with actual SF, and the mortal sin of claiming Star Trek invented SF fandom.
I mean, I’m a smidge offended 
, but I reserve spittle for more weighty and invective-worthy subjects.
How about a link to a costumer ranting about (and getting facts wrong on) all those kids today calling it cosplay?
One of my most recent Let’s Make MrAtoz Feel Old experiences happened when a young lady in her late teens was shocked to find out that I, an old codger of fifty, knew the word “canon.” As far as she knew, that word was invented for anime.
Everything is older than you think it is.
Obviously there were Sci Fi fans before Star Trek and I know there were sci fi conventions before Trek conventions and you can find examples of people doing all of these things but Trek fans in the 60s and 70s created the templet and wrote the rules almost all modern fandom follows today. They made it more mainstream and turned it into something the average person may have heard about.
ETA: Sherlock Holmes is a good one I hadn’t thought of. Good point.
Still no.
One might argue that the whole idea of a canon defining what is and isn’t part of a fictional universe started much much earlier, with the First Council of Nicaea. 
Basically the main difference is that a costumer is interested in creating or re-creating a costume, while a cosplayer is interested in re-creating or creating a character.
IMHO, that is a bit of an artificial division.
Congratulations. You two have just committed fandom.
Please don’t get any on the sofa.
Look up Goethe’s The Sorrows of Young Werther: there was merchandising, fanboys were making pilgrimages and cosplaying that shit in 1775. It was banned in some places because of copycat suicides.
Did you see that episode of History Bites? Hilarious.
Theology was the original fan-wank.
Is that anything like a template? :dubious:
It’s hard for me to say positively, but from what I understand, slash fiction as it’s currently recognized supposedly originated with Star Trek fanzines in the US (it seems to have emerged entirely separately in Japan.) The story is that the term “slash” came from the marking between Kirk and Spock’s names to indicate a relationship (Spock/Kirk), versus a + mark to indicate the two together in stories as just friends and coworkers.
Whether this was a great contribution to fandom or a horror that can never be undone is up to the reader.