Flattop is
Timothy Leary. The song was inspired by Leary's
slogan in his campaign for governor of
California. "Come Together, Join the Party", inspired by the
I Ching. Lennon gave Leary a demo tape, which Leary had played on alternative radio stations.
Leary first heard the studio version while in prison on
marijuana charges.
Information paraphrased from Steve Turner's book A Hard Day's Write, not to be confused with Lennon's surreal book In His Own Write.