The clown Pagliacci sings this lament in Leoncavallo's opera, but the aria has also been commandeered to express sadness and frustration throughout popular culture. It's been sung to particular acclaim by Placido Domingo, who also appeared on The Simpsons as himself (Domingo turns 71 on Sunday).
In The Simpsons' episode "The Italian Bob," Sideshow Bob, Krusty the Clown's sidekick, sings the popular aria:
In this ad for Coca-Cola, Pagliacci eyes a bottle of Coke off stage. Instead of applauding for his singing, the crowd cheers when a little boy brings him the Coke.
In classic all-encompassing style, the Seinfeld episode "The Opera" draws all the characters, including Crazy Joe Devola, into Kramer's scheme to see a performance of Pagliacci.
The aria is alos briefly quoted as part of an opera-parody episode of "Hey Arnold!"