It is well-known that The Beatles were a quartet also known as the "Fab Four." But debate has been raging for decades about the fifth Beatle — an unheralded, unnamed person who was somehow instrumental to the band's staggering success. Who deserves the title? Dozens of hangers-on and associates have staked out the name, but there are six men who are most often mentioned in fifth Beatle conversations: two who were members of the band in its early days as a quintet and four who were longtime behind-the-scenes collaborators.

Stuart Sutcliffe perhaps has the most claim to the title — he was the fifth member of the band from 1960 to 1961, and he wasn't replaced after he left. A friend of John Lennon's from the Liverpool College of Art, he was more artistically than musically inclined, but he became the Beatles' original bassist and played clubs with them in Hamburg, Germany. His "mop-top" hairdo, sunglasses and skinny pants influenced what would become the Beatles' signature style. When the rest of the group went back home to Liverpool in 1961 (and subsequently made it big), he stayed in Hamburg, and Paul McCartney took over as bassist. Sutcliffe died of a brain aneurysm only a few months later at the age of 21.

Pete Best was the Beatles' original drummer, a member of the band along with Sutcliffe. He returned to Liverpool with the group in 1961 but was fired a year later and replaced by Ringo Starr. The official story is that the band's first studio producers wanted to ditch Best for a more experienced drummer, but rumors suggest he was let go for getting more than his fair share of attention from female fans. By all accounts, the firing was not handled well, and he successfully sued the Beatles in 1968 for libel because of a Playboy article in which Starr claimed he abused drugs.

By all accounts, the firing was not handled well, and he successfully sued the Beatles in 1968 for libel because of a Playboy article in which Starr claimed he abused drugs.