The Fifth Beatle

Nothing wrong with this as a quiz question, but the epithet 'the Fifth Beatle' has long been one of the most over–used clichés in the book.

Paul McCartney said, following George Martin's death in 2016, that if anyone was the Fifth Beatle, it was him. He'd previously said the same thing about Brian Epstein.

On the Beatles' induction into the Rock and Roll Hall of Fame, in 1988, George Harrison said that there were only two "fifth Beatles": Derek Taylor and Neil Aspinall. Derek Taylor was a journalist, who became the Beatles' press officer; Neil Aspinall was a schoolmate of McCartney and Harrison (and a close personal friend of Pete Best), who owned a Commer van and became the Beatles' roadie, later becoming CEO for Apple Corps – a position he held until 10 April 2007.

Ringo Starr's thoughts on the Fifth Beatle don't seem to have been recorded; but he did tweet, on George Martin's death: "Thank you for all your love and kindness George peace and love ... God bless George Martin peace and love to Judy and his family love Ringo and Barbara George will be missed."

John Lennon generally refused even to entertain the concept of a Fifth Beatle. (He even denied, in a lyric from the Plastic Ono Band album, that he believed in Beatles.)

The Liverpudlian comedian and musician Mitch Benn (probably best known for his appearances on Radio 4's The Now Show – at least, he is to me) performed a show at the Edinburgh Fringe in 2013 entitled Mitch Benn is the 37th Beatle. He listed the other candidates "in descending order of Beatledom":

5th		Pete Best – actually the Fourth Beatle, recruited to play drums following the demise of the Quarrymen; replaced by Ringo in 1962 (by Brian Epstein, on advice from EMI technicians)
6th		Stuart Sutcliffe – the actual Fifth Beatle, recruited shortly after Best to play bass guitar; left in July 1961 to stay in Hamburg with the photographer Astrid Kirchherr, to whom he had become engaged, and to concentrate on his painting. He died of a brain haemorrhage, in Hamburg, in April 1962
7th		Tony Sheridan – singer backed by the Beatles on stage in Hamburg, and on some early records
8th–12th		The other original Quarrymen – including washboard player Pete Shotton, who later managed a supermarket that was owned by Lennon and George Harrison, and went on to found the Fatty Arbuckle's chain of restaurants
13th		Andy White – session drummer who replaced Ringo on the US single release version of Love Me Do
14th		Jimmie Nicol – drummer who stepped in for a series of concerts in 1964, at the height of Beatlemania, when Ringo was suffering from tonsillitis
15th		Billy Preston – the only artist to receive a joint credit on a Beatles single: Get Back was credited to The Beatles with Billy Preston
16th		Eric Clapton – played a guitar solo on While My Guitar Gently Weeps; also played on solo recordings of all four Beatles, after their split
17th		Brian Epstein – the manager who turned the Beatles into global superstars
18th		George Martin – producer of nearly all of the Beatles' recordings (the Let It Be album was produced by Phil Spector, and the songs Real Love and Free as a Bird by Jeff Lynne)
19th		Derek Taylor – the journalist who became the Beatles' press officer
20th		Mal Evans – assistant road manager; shot dead by police at his home in Los Angeles in 1976
21st		Neil Aspinall – schoolmate, roadie and business associate; see above
22nd–25th		Badfinger – the first group signed to the Apple label (1968)
26th		Jeff Lynne – close collaborator of George Harrison, and co–producer of the Beatles' Anthology reunion singles Free as a Bird (1995) and Real Love (1996)
27th–32nd		Monty Python – "a continuation of the spirit of the Beatles", according to George Harrison
33rd		Neil Innes – musical collaborator with Monty Python, and co–creator (with Python's Eric Idle) of the Rutles
34th		David Caitlin–Birch – Paul in the Bootleg Beatles
35th		Neil Harrison – John in the Bootleg Beatles
36th		Elvis Costello – Paul McCartney's songwriting collaborator on the Flowers in the Dirt album (1989)

Mitch Benn doesn't even mention Klaus Voormann, Murray 'the K' Kaufman, Allan Williams, Apu Nahasapeemapetilon, or George Best.

Klauss Voormann played bass guitar for the Beatles in Hamburg, after Stuart Sutcliffe left the band. When McCartney left in 1970, precipitating the Beatles' break–up, Voormann was mooted as a replacement. After the breakup and until 1976, he played on almost every solo album recorded by the other three Beatles. He also drew the main cover illustration for the Revolver album.

Murray Kaufman, a.k.a. Murray 'the K', was a New York radio DJ who promoted the Beatles during their first US tour. He possibly invented the term 'the Fifth Beatle' – to describe himself. According to CNN Entertainment, the four actual Beatles were happy to go along with this self–promotion.

Allan Williams was the Beatles' de facto first manager. He recruited Pete Best, secured the band their Hamburg residencies, and drove the van in which they travelled there. He parted company with them in 1961, after they refused to pay him commission for a later trip to Hamburg. Brian Epstein contacted him a year later to check that there were no remaining contractual ties and to seek his opinion of the band. Williams advised him "Don't touch them with a f***ing barge pole".

Apu Nahasapeemapetilon is the proprietor of the Kwik–E–Mart convenience store in The Simpsons – best known for his catchphrase, "Thank you, come again." In the episode Lisa the Vegetarian, when Lisa Simpson is struggling in her efforts to avoid eating meat, Apu introduces her to Paul and Linda McCartney. He claims to have met the Beatles while studying meditation with Maharishi Mahesh Yogi. He jokes about being "the Fifth Beatle", at which Paul rolls his eyes and sarcastically replies, "Yeah, sure you were, Apu."

George Best was famously dubbed 'El Beatle' by the British press after Manchester United's 5–1 victory over Benfica, at the Estádio da Luz, in the quarter–finals of the 1965–6 European Cup. He also shared a surname with Mitch Benn's nomination as the actual Fifth Beatle.