George Harrison was the Beatles' acknowledged lead guitarist, but others subbed for him as far back as 1964's "You Can't Do That." There was also the trio approach employed on 1969's "The End," as first Paul McCartney, then Harrison and finally John Lennon traded two-bar solos three times.
In between, Lennon and McCartney would occasionally take over, even if Harrison continued to mime their guitar solos onscreen for "Another Girl" from the Help! movie and the promo clip for "Paperback Writer" – both of which were actually performed by McCartney.
This created some confusion, sometimes even within the group. "I don't think I was playing the guitar feedback" on 1967's "It's All Too Much," Harrison told Billboard in 1999. "As I say, I was playing the organ, so I think that was probably Paul that did that."
Source: ultimateclassicrock.com