For the uninitiated, there is an older meme known as Rule 34 of the internet: If it exists, there is porn of it. No exceptions. (Reader beware: do not test Rule 34. Whatever you think might be too far-fetched, it’s out there, and if you think it’s not, do you want to find out the hard way that it’s not?)
There is a newer meme similar to Rule 34: There is a subreddit for everything.
Writing prompt: You always thought the idea that there’s a subreddit for everything was a joke. Then you found r/tailcare where humans discuss tips for tail hygiene and maintenance. At first, you think this is maybe a furry thing, but the more you read, you start to suspect these are humans with actual tails. When you pm someone about it, they send their condolences and ask if you’ve seen r/tailectomies, a subreddit for people whose tails have been surgically removed. If this is a subculture or con, it’s too big to have been hidden this well. Something happens that finally clicks: you’ve found a subreddit from an alternate universe.