The Fab Four Hairdos refers to the iconic hairstyles of the Beatles, a British rock band that rose to fame in the 1960s. The four members of the band, John Lennon, Paul McCartney, George Harrison, and Ringo Starr, each had their own distinct hairstyle. John Lennon's was a shaggy mop top, Paul McCartney's was a bowl cut, George Harrison's was a longer, wavy style, and Ringo Starr's was a short, spiky cut. The term 'MOPS' is an acronym for the four hairstyles, with each letter representing one of the four styles: M for mop top, O for bowl cut, P for wavy, and S for spiky.