Let me first of all say that I completely love this movie and its soundtrack too. Seriously, it's one of my favorites ever. It has lots of mentions of the Beatles, but it also has many sort of references/parallels, too:
-Jimmy = John, the moody troubled guy who breaks away from the band in the end
-Lenny = Paul, the romantic optimist who tried his darndest to keep the band together
-Guy = Ringo, the popular drummer who everyone liked and was the one no one ever had too much of a problem with. Also Guy's shades= Ringo's rings
-Ethan= is George Harrison, the quiet loner one who was probably the furthest remove from the group and ultimately left the band first (like George did with the Beatles).
-Fay = Cynthia, the neglected girl who in the end loses Jimmy to other women and his music
There are other parallels to the Beatles:
-There hit song is a sped up version of a slow ballad, like Please Please Me.
-Jimmy throws up before their TV appearance, like George did before Ed Sullivan.
-Their TV appearance on "Hollywood Showcase" is like the one the Beatles had on "Ed Sullivan", complete with the dress and the stage set up, even the shots are the same.
-They are hounded by girls after a show, just like Beatlemania.
-The initial drummer is replaced, like the Beatles did when they replaced Pete Best with Ringo Starr.
-The "careful girls he's engaged" quote for Jimmy was similar to John's "Sorry girls he's married" on "Ed Sullivan".
-They go into making movies, like the Beatles did.