"When I'm Sixty-Four" is a song that appears in Sgt. Pepper's Lonely Hearts Club Band. It was written by Paul McCartney but was credited as Lennon/McCartney. It was recorded on December 6-21, 1966 and released June 1, 1967.
"When I'm Sixty-Four" was written by McCartney when he was 16 and is one of the first songs he ever wrote.
During their Cavern days, The Beatles added on a few more words and would play it whenever the amplifiers broke or the electricity went down.