clean
Explanation
The Joke
The comic shows a scene where someone is impressed when visiting a guy's place for the first time, commenting, "Wow, I'm always impressed when I see a guy's place for the first time and it's super tidy." The man responds modestly, saying something like, "Oh shucks, this is just how I live. Things I don't use regularly go back in their environments." But then the visitor asks to check how clean his keyboard is -- a reasonable litmus test for true cleanliness -- and the view of the keyboard reveals it to be absolutely filthy, exposing that his apparent tidiness is a carefully maintained facade.
The Humor
The joke trades on the well-known phenomenon of people (especially stereotypically messy people) frantically cleaning their homes before guests arrive, creating an illusion of habitual tidiness. The keyboard serves as the perfect lie detector because it's something most people forget to clean even during a pre-visit cleaning spree. It's the one object that reveals true hygiene habits because it accumulates grime from daily use and is rarely thought of as something guests will inspect. The comic plays on the gendered expectation that men's living spaces are messy, the performative tidying people do before visitors arrive, and the idea that there's always one telltale detail that gives away the truth.