John Lennon's lyrics were his first overt reference to LSD in a Beatles song. The song can be seen as Lennon teasing Paul McCartney about not taking acid.
In 2004, Paul McCartney did an interview with the Daily Mirror newspaper where he explained that drugs influenced many of The Beatles' songs. He singled this one out as being about acid (LSD), but also said that people often overestimate the influence of drugs on their music.
The line "She's a big teaser" was written as "She's a prick teaser."
Lennon: "Day trippers are people who go on a day trip, right? Usually on a ferryboat or something. But the song was kind of - you're just a weekend hippie. Get it?" (thanks, Bertrand - Paris, France)
A short promotional film of The Beatles lip-synching to this song was made for the TV special The Music Of Lennon and McCartney, which first aired December 17, 1965 in the UK. It was one of the first music videos. (thanks, Bertrand - Paris, France)
Lennon wrote this after their record company demanded a new single. The Beatles were not that happy with the way this song turned out because they had been forced to come up with a new single. (thanks, Adrian - Wilmington, DE)
Jimi Hendrix sometimes covered this at his concerts.
This was released as a double A sided single with " We Can Work It Out." It went to the #1 position in the UK but only went to #5 in the US. In fact, "We Can Work It Out" got more airplay in the US. In America, the single was released on the same day as the Rubber Soul album, although neither song was on that album. The Beatles were popular enough to support the output.
James Taylor did a cover version on his album Flag. (thanks, Jake - New Rochelle, NY)