In binary "Diffuse these latents with these tokens."
Human: No, please, I am more than just a human!
I remember some website having them as a gag. It would show you some complex math equation but the answer was always 0. If you failed enough, because you didn't get the joke, you'd get a (1 - 1) or something simple that still worked out to 0. Sometimes you'd get a [zero] as a regular captcha.
I don't even remember what the site was, or was about, but I still remember that captcha.
That feeling when you discover your best friend is a human.
XOR a bit-flip of a few hexadecimal strings hidden in base64 after overflowing them through a buffer with a variable size that changes every hundredth of a second.
Ended up at a robot only dance party in deep playa at Burning Man this year and indeed you did have to solve a prove you aren't human captcha to "get in"