The song with the longest title is "I?m a Cranky Old Yank in a Clanky Old Tank on the Streets of Yokohama with my Honolulu Mama Doin? Those Beat-o, Beat-o Flat-On-My-Seat-o, Hirohito Blues" written by Hoagy Carmichael in 1945. He later claimed the song title ended with ?Yank? and the rest was a joke.
