I'm admittedly not so up on my Beatles trivia, but I know enough about songwriting that the practice of placeholder lyrics is commonplace. That said, getting an artist to revisit a song in its nascent form is often a task left for box sets and reissue extras. Kudos then to Fallon for getting a Beatle (no less) to perform "Yesterday" with one of its original couplets, "Scrambled eggs / Oh my baby how I love your legs" ... and a few updated lines about waffle fries and wings.
Macka also dusted off his 1982 tribute to Lennon "Here Today" from his Tug of War LP -- appropriate considering the 30th anniversary of Lennon's death on December 8.