There's a theory that the boneless person who is just skin, with a pained expression on his face, in the Sistine Chapel is a self-portrait of Michaelangelo. He painted it under extremely challenging circumstances at one point the Pope beat him with a switch because it was taking too long in his opinion.
I'm just working through something... I've liked this one since I was a kid...
btw I recently watched that movie Conclave which takes place in the Sistine Chapel, where the The Last Judgment is located, and a couple of times people gaze upwards at the paintings for inspiration...