Written during either late 1965 or early 1966, it includes comparisons of the hallucinatory effects of psychedelic drugs such as Magic Mushrooms with the imagery found in the fantasy works of Lewis Carroll: 1865's Alice's Adventures in Wonderland. Events in these books, such as changing size after eating mushrooms or drinking an unknown liquid, are referenced in the song.
Set to a rising crescendo similar to that of Ravel's famous Boléro, and having a strong Spanish influence to it, the music combined with the song's lyrics strongly suggest the sensory distortions experienced with hallucinogens and the song was later utilized in pop culture to imply or accompany just such a state.