While teaching Spike math one afternoon, Twilight comes up with a solution of 'sixty-nine'. Spike can't stop laughing enough to tell her what's so funny, so she's going to find out.
Oh, she will find out.
Edited by Syeekoh
Preread by RainbowRick, thanks to both of you!
This was originally meant to be my sixty-nine follower special, but other stuff came up and...yeah. I eventually got around to it. Enjoy!