The specific phrase originates from a well-known 3440x1440p ultrawide wallpaper featuring a macro-style digital illustration. It typically depicts a mechanical keyboard switch where the internal stem is replaced with a piece of sushi (often nigiri or a maki roll).
There is even an interactive version on Wallpaper Engine where the sushi switch can be "clicked" on-screen, accompanied by mechanical keyboard sound effects. Physical "Sushi" Keyboard Gear
Known for their highly detailed "Sushiville" resin keycaps that look like realistic miniature seafood.