Faerie’s Aire and Death Waltz and Touhou
This is a shortie but the internet is a weird, weird place. You may have seen this before:
It’s not only impossible to play but inadvisable… as this video demonstrates. Goofy sheet music / sheet music as a visual medium is a pretty interesting rabbithole of its own, of course! And @awesomonster has also clued me in to Synthesia, which is its own special weird virtual sheet music hell. She recommends searching youtube for the words “IMPOSSIBLE REMIX” if you want to find more.