Pack up your troubles in your old kit bag
From Tardis Wiki, the free Doctor Who reference
"Pack up your troubles in your old kit bag" was a song known on 21st century Earth (PROSE: Winner Takes All) and to 51st century ex-Time Agent Captain Jack Harkness. Its chorus contained the lyrics "smile, smile, smile". Jack was singing a florid rendition of the song while alone in the TARDIS console room when a distress call was picked up originating from the Novrosk Peninsula in Russia, and Jack didn't notice the warning beeps until he was halfway through the next chorus. (PROSE: The Deviant Strain)
Behind the scenes
It is a World War I marching song.
