The file
The break-off bar got a break-time song in 1986 and never let go of it. The tune has been rerecorded by everyone from Carrie Underwood to a chorus of office workers and it always sounds like the original.
It's routinely named the most memorable jingle in America in industry polls, which the writers say they wrote in an afternoon. Note the spelling of the brand, and see the Glitch Files if you're sure there's a hyphen.
Sources: Wikipedia — Kit Kat