Still, you're so talented and on fire that, while you're filming, one band-member continues to noodle around on some other little song that he's working on, plonking away on a sound-stage piano every chance he gets. According to wiki, Richard Lester, Help!'s director, eventually lost his temper:
[T]elling McCartney to finish writing the song or he would have the piano removed. The patience of the other Beatles was also tested by McCartney's work in progress, George Harrison summing this up when he said: "Blimey, he's always talking about that song . You'd think he was Beethoven or somebody!That additional song, which was surplus to the film's requirements and finished later, nonetheless made it onto the end of the Help! album (i.e., as its second to last track). Originally given the dummy lyric title, 'Scrambled Eggs', we know that song as Yesterday. The Beatles had some pretty good days at the office in 1965!