As you all know, today, May 4th, is the official Star Wars day! As it is a special day and discourse does have certain capabilities, a Star Wars theme has been installed! Keep in mind, this theme will be available today and tomorrow only, so use it while you can! (And yes, it is a dark theme)
In order to change to this theme, you must first reload the page. Then, go to the hamburger menu from any page, scroll down to Theme Selector and select Star Wars . The other way to do this is to go to your profile → preferences → interface → Theme → select Star Wars. The theme will then show up!