Paul McCartney and Frank Sinatra are musical icons in their own right. However, did you know that McCartney wrote a song for the Sgt. Pepper album that was initially for Sinatra? The musical group and Sinatra had a great appreciation for each other, with Sinatra calling George Harrison's "Something" 'one of the best love songs written in 50 to 100 years.' When McCartney was growing up in the 1950s, he often looked to Sinatra as a source of inspiration. McCartney dreamed of writing for crooners like him who were considered legends in the music industry. \u201cBack then I wasn\u2019t necessarily looking to be a rock \u2018n\u2019 roller,\u201d he shares via The Beatles\u2019\u00a0Anthology. Well, that dream once came true. Sort of. Paul McCartney and his original song for Frank Sinatra McCartney's personal favorite album is Sgt. Pepper's Lonely Hearts Club band and one of the songs on there was initially for Sinatra. \u201cThere were records other than rock \u2018n\u2019 roll that were important to me. And that would come out in the Beatles doing songs like \u2018Till There Was You,\u2019\u201d McCartney says. RELATED: The Story Behind The \u201cSgt. Pepper\u2019s Lonely Hearts Club Band\u201d Album Cover \u201cWhen I wrote \u2018When I\u2019m Sixty Four\u2019 I thought I was writing a song for Sinatra,\u201d he says. \u201cI wrote when I was sixteen \u2014 it was rather tongue-in-cheek \u2014 and I never forgot it.\u201d It wasn't until eight years later when McCartney would revisit that song and record it for the upcoming Beatles album. While Sinatra would never sing that song, he did cover another recognizable Beatles song... What's even more amazing is that the version that ended up on Sgt. Pepper is almost exactly had McCartney originally intended the song to sound. \u201cI wrote \u2018When I\u2019m Sixty Four\u2019 vaguely thinking it would come in handy in a musical comedy or something,\u201d he says. Interestingly enough, John Lennon was never a fan of the song. He even said to Playboy\u2019s David Sheff in 1980, \u201cI would never dream of writing a song like that. There\u2019s some things I never think about, and that\u2019s one of them.\u201d While Sinatra would never sing "When I'm Sixty Four," he did end up covering one of his hits... the recognizable tune "Yesterday." Check out the remastered version of "When I'm Sixty Four" below.