What's not to love about this gallery of images from the 1966 World Science Fiction Convention in Cleveland, OH? The cameras may have acquired color and the cosplay may have become a bit more sophisticated, but the spirit of the players seems to have remained unchanged.
These images were taken by the late photographer, and sci-fi mega-fan, Jay Kay Klein. You can see the massive collection of Klein's photos and papers of science fiction fandom on the Calisphere website.
Image: Composite of images from the Jay Kay Klein collection, via Cosplay Central