I’ve thought for a long time that there was a great eposodic book (or possbily radio doc series)  in having a chapter on each of the peopl that have a some point or another been called the “fifth beatle” – anyone is welcome to have a go, I’ll never get round to it. Neil Aspinall’s death has reminded me – let’s see how many we can think up:

Pete Best

Stuart Sutcliffe

Brian Epstein

George Martin

George Best

Billy Preston

Murry The K

(actually there are tons on this Wikipedia page)