The 'You Stupid Slut' meme features Dennis Reynolds from the sitcom 'It's Always Sunny in Philadelphia,' portrayed by Glenn Howerton. The image is captured during a moment of intense, unhinged road rage while Dennis is driving (and famously eating cereal). While the line is often a misquotation or variation of the 'Jane, you ignorant slut' SNL bit, it became a viral sensation for Dennis's uniquely vein-popping expression of fury. It is widely used to react to situations where someone has done something incredibly annoying, or when an inanimate object—like a computer or a slow internet connection—fails at a crucial moment.