I had knee surgery as a teenager. The dr brought me a sharpie and told me to circle the correct knee and put an X on the other then he left the room. So did exactly as instructed.
Then I drew arrows to the circle and wrote
"Operate here" and drew more Xs on the other leg and wrote "Do not touch". I sat there bored for another 30 minutes writing random stuff all over my body like "You can't have my appendix" and "Why are you looking up here?
Focus on the knee". I even had my mom write on my back something like "If you can read this, wrong side. Flip me over."