No Doy is a well-known typographical error and inside joke originating from the animated television series The Simpsons. The phrase first appeared in the episode "Bart Gets an F," which aired as the first episode of the second season on October 11, 1990.
During a scene where Homer Simpson is suffering from sensory deprivation and cabin fever after his television and beer are taken away, he writes a sign that reads: "NO TV AND NO BEER MAKE HOMER SOMETHING SOMETHING." Below this main text, a smaller, separate sign was intended to read "NO, DUH!" as a sarcastic interjection, implying that Homer's agitated state was an obvious consequence.
However, due to an error in the creation of the animation prop or background art, the sign was mistakenly rendered as "NO DOY." This unintentional misspelling quickly became an identifiable error and a source of humor among dedicated fans of the show. Over time, "No Doy" evolved into a minor catchphrase or a reference used to sarcastically acknowledge something obvious, or simply to refer to the famous typo itself within The Simpsons fandom. It stands as an example of how an accidental detail can become a memorable part of pop culture history.