I’ll go first: r/kitty. One of the hundred grillion cat subs back on Reddit, the culture in this one was you posted a cat picture, and the only word allowed in the title or in any comments or replies was “Kitty.”
Someone is using that subreddit for covert communications, I just know it. Either on the level of “if u/PM_me_your_nostrils posts an orange cat, we attack at dawn!” or there’s some steganography going on with the pictures, but that subreddit was too stupid to be as active as it was.
Years ago I had fun with “what if the US never actually went to the moon”. I did not believe it, it was just a nice plot idea, we even made a pen & paper oneshot about it. Nowadays I have no whatsoever fun in thought experiments like this, because the real threat of someone believing it to be true. I want to enjoy “birds aren’t real” or “giraffes do not exist” or … the worst is flat earth. It started out as a joke and now idiots try to proof the earth is flat, proof by accident it isn’t and then question rather their methods than their belief system. We just can’t have nice things.