The line comes from Napoleon Dynamite, the 2004 independent comedy about an awkward Idaho teenager, and is spoken by its title character. Short, blunt movie quotes like this one became popular on soundboards because they work without any setup, and this clip spread in the same way through reaction videos and meme edits. Fans still use it because Napoleon's deadpan style is instantly recognisable, and a single insult delivered so calmly fits almost any moment of obvious stupidity online.