Cosi fan tutte, the third of the great "Da Ponte" operas of Mozart and librettist Lorenzo da Ponte, premiered in Vienna to great acclaim in 1790. The story revolves around two couples, Ferrando and Dorabella and Guglielmo and Fiordiligi. Under a bet from their mentor and confirmed old bachelor, Don Alfonso, the two men disguise themselves as "Albanians" and test their girlfriends' fidelity by courting the opposite girl. 

After a series of awkward situations worthy of a modern-day sitcom, the lovers learn a very important lesson: "All are alike" in that everyone is a teeny bit unfaithful every once in a while. Cosi fan tutte is now one of Mozart's most frequently performed operas.