When I first discovered Size Tumblr (RIP) back in 2015, one of the stumbling blocks for me was how much size art was actually repurposed fan art, usually of characters from some anime or video game with which I was unfamiliar. Here I was, looking for anonymous size interaction, and I was confronted with names and worlds with seemingly unrelated backstories. Often as not, the characters were from universes where size differential was unknown or even improper to the genre. But the artist (or their followers) really liked those characters (or the show/game) and saw no reason not to make one of them giant or tiny and see what they looked like.
Eventually I determined that many artists start out copying others’ characters and styles before creating their own work (that was when I learned that “OC” stands for Original Character), so if they had a size kink it was natural that they would experiment with established characters first before creating their own original giants and tinies. It all clicked for me when I realized it was the graphical equivalent of fanfiction.
It still kind of irks me when characters from a “normie” universe are suddenly thrust into a size encounter. Realistically such characters would focus entirely trying to explain on the supernatural size phenomenon rather than have the sizey sexytimes the fanartist might be hoping for. I have an easier time when the genre already allows for magic or fantastic technology, so I have some idea of how those characters will react to size differential (hopefully in a pervy way). It’s a lot easier to swallow Hermione fudging a spell or a malfunctioning transporter than, say, Dr. House contracting a rare shrinking disease.
Anyway, in Decmber 2018 Tumblwintr blew, sharply curtailing the amount of size-crossover fanart to which I was exposed. Partly in tribute to what I learned from my Tumblr experience (but mostly in response to a prompt from @MightyTinyGiant), I composed Played, my Firefly fanfiction. It starts out F/m (Saffron/Mal), but it’s mostly F/f (Inara/Saffron).