Came across this while surfing Youtube:
The Beatles - Songs Sung by the Wrong Beatle (Full Album)



Description borrowed from here:

Fresh from youtube, this was uploaded just a couple of weeks ago. Love the concept. John and George did not do lead vocals on Get Back; they do in this album. Some were sung live in concert, e.g. George doing In My Life in his 1974 tour; then Paul, A Day In The Life/Give Peace A Chance, which I think he first sang live in Ukraine in the early 2000s; and then Ringo, Love Me Do, in his 1990s tour. Some songs were playfully performed in between recording sessions. This compilation at the very least demonstrates how the Beatles appreciate each other’s composing efforts. Listen to Paul doing I’m So Tired and John, I’ve Got A Feeling. They should have included Oh, Darlin’! with John in the lead vocals. For his part, George’s interpretation was always particularly different.