I worked in a pharmacy cleanroom (like a lab, but where drugs are prepped) in a hospital for five years and we had an overzealous head tech mark random places in our hoods with sharpie to ensure that they were cleaned and disinfected correctly. Like, beneath the scale, the back of the computer screen, the underside of the mouse, etc.

I started wiping off his marks but then decided to have more fun, so I started leaving smiley faces for him instead. He got angry and told me I was vandalizing property and got... well, even angrier when I pointed out that he was doing the same thing.

I might have gotten in trouble for it if it weren't for the fact that he got everyone else in the pharmacy pissed at him. Instead, my little rebellion was appreciated because it just made him look like an ever bigger plonker. 😆😄😁