The name of Lee Marvin's motorcycle gang is "The Beetles." Although it has never formally been acknowledged as an inspiration for the name of the 1960s rock band, the scene from the movie where Marvin introduces The Beetles is used at the beginning of The Beatles Anthology.
Based on a 1951 short story in Harper's Magazine entitled The Cyclists' Raid, which in turn was based upon a real-life incident in Hollister, California in 1947. The actual incident, however, bore little resemblance to the events depicted in the movie. Although spirited, the cyclists did not run amok or become violent. In fact, the bikers were invited back to Hollister over the July 4, 1997 weekend for a fiftieth anniversary celebration of the original incident.
Pigeon, a member of the Black Rebels Motorcycle Club led by Johnny Strabler (Marlon Brando) is played by an uncredited Alvy Moore. Moore would achieve greater recognition some twelve years later playing the absent minded county agent Hank Kimball on Green Acres.
This was the first film in which the manufacturer's logo on motorcycles was not blanked out. Johnson Motors, who imported Triumphs into the USA, protested at their product being linked with Brando and his Black Rebels, but the association served them well.
Marlon Brando's motorcycle is a 650cc Triumph Thunderbird. From stills, its registration number looks like 63632. Lee Marvin also owned a Triumph 200cc Tiger Cub upon which he competed in desert races. 'Jr Gil Stratton' was featured in a print advertisement for Triumph motorcycles in 1963. He later became a well-known TV sports reporter in Los Angeles for decades.
Lee Marvin could not ride a motorcycle at the time of filming, but determined not to be bettered by the star (Brando) he quickly learned, later becoming a keen competitor on his Triumph 200cc Tiger Cub in desert races.
A popular still from the film shows an off-set Marlon Brando astride a Matchless twin cylinder motorcycle, it's 'M' logo gas tank badge being secured upside-down to resemble a 'W'. This was stunt rider 'Wally Allbright''s motorcycle.