One of the parts of making a telescope mirror is what's called the "Sharpie Test", where you draw all over the mirror with a permanent marker (you can guess what brand usually gets used) to make sure you're working the entire surface of your mirror well as you grind it. They describe the test in detail on one of their tutorials over on gotgrit.com.
Well, I like to have some fun with my Sharpie tests, I get tired of just drawing plain old grid patterns. So I like to draw other things. Pizzas are a favorite. I also draw all sorts of cartoons on the mirror. They only last a few minutes, so it's very ephemeral as art goes.
My wife suggested I take some pictures, and after reminding me of the idea enough times I finally took pictures of a couple of my Sharpie test patterns, and now I've finally posted them. Here you go.
Not all my drawing have cats, I just got more pressure into taking pictures when they had cats.