Paul McCartney (in 1969) - We were sitting in the studio and we made it up out of thin air...we started to write words there and then...when we finished it, we recorded it at Apple Studios and made it into a song to roller-coast by.
John Lennon (in 1980) - "'Get Back' is Paul. That's a better version of 'Lady Madonna.' You know, a potboiler rewrite."