Actor Allusion: Paul's grandfather is frequently referred to as "clean" because the actor, Wilfrid Brambell, played a "dirty old man" in Steptoe and Son (which begat the American versionSanford and Son). These jokes would often go over American fans' heads, but British audiences would've gotten the references immediately.
And according to the extras on the DVD, Brambell was a meticulously clean and well dressed man in real life.
Creator Backlash: While he doesn't dislike the film by any means, Richard Lester has often said that it's annoying to have film history classes lecture about how most of the entirely accidental filming techniques used were, in fact, well-orchestrated cinematography worthy of an art-house picture. When told that this film made him "the father of MTV," he replied "I want a DNA test."
Fake Brit: More like "Fake Scouse". Actor John Junkin, who plays the Beatles' roadie Shake, was born in Ealing, a suburb in West London but was told after being cast to pretend to be from Liverpool when he met the Beatles to make them feel more at ease. The Beatles were annoyed at first when they find out a few weeks later but forgave him.
The Red Stapler: Demand for the Rickenbacker 360/12 12-string guitar skyrocketed after George Harrison used one throughout the movie.
Romance on the Set: George Harrison met his first wife, Pattie Boyd, while shooting this film. She played the blonde schoolgirl who says "Prisoners?" when Paul tries to flirt with her on the train.
Studio Hop: The film was originally a United Artists release, and was licensed from its original owner, American film producer Walter Shenson. After UA lost the rights in 1979, Shenson regained the rights to the film, and since then, three different Hollywood studios have released it: Universal Pictures in 1982, Miramax Films in 2000, and Janus Films in 2014.
In the very first shot of the movie, George accidentally tripped and fell, and Ringo accidentally fell on him. The falls and the Beatles' laughter about it lent the shot an increased sense of energy and motion, so that footage was left in.
John wasn't meant to be in the bathtub when George was teaching Shake how to shave, but when Lester found Lennon already there, they decided to work it in.
Director of Photography Gilbert Taylor said that the sped-up aerial shots in "Can't Buy Me Love" came about because the battery in his camera started to die, causing the footage to be "undercranked" and fast motion. When director Richard Lester saw the rushes of the footage, he immediately arranged for more sped-up aerial shots.