Star Trek fans were some of the earlier cosplayers. Trekkies were wearing Starfleet uniforms and Vulcan ears to conventions decades before the word “cosplay” was a thing. My father has a book called the Starfleet Technical Manual published in the 70’s that is basically an official guide for fans to build screen accurate costumes and props from, including sewing patterns for the various tunics and wrist-length dresses and a page of color swatches, plus dimensional drawings of tricorders, phasers and communicators.
And the public at large in the 1970s wasn’t ready for that yet.