The wah-wah teacher voice debuted in A Charlie Brown Christmas in 1965, when the producers of the Peanuts TV specials decided adults should never speak intelligibly on screen. A trombone played with a mute became the voice of every grown-up, mumbling gibberish the kids cheerfully ignore. The gag stuck across decades of specials and films, and the sound escaped into meme culture as universal shorthand for blah-blah-blah. Today it lives on in GIFs, reaction videos and edits mocking lectures, meetings and nagging.