The original story behind this video is nothing much at all. I may have imagined this because I can't find any trace of it anywhere: I saw a post online about someone's sick cat, I think it had a stomach bug or something similar, and it said "[my cat] got the rotten," referring to the disease as "the rotten," which I loved.
Note to self
A bit later, I wrote down the phrase on a piece of paper. As soon as I could, I started drawing the sprites and backgrounds you see in the video. The face at the end was actually part of the background and I had to do a bit of editing and redrawing when I made the second video. The music, if you wanna call it that, was made specifically for the video.
How I got the idea for the video game format and such, I don't know.