A friend of mine, David Lipschutz, and I, were recently joking around on Facebook and decided to play a quick game of Parody Sequels- where you each try to one up each other on the best (by which I mean WORST) parody sequel titles to musicals that have no need whatsoever for sequels. There actually is some precedent for sequels to musicals, though they generally wind up in the rubbish pile of musical history:
Annie Warbucks (the sequel to Annie)
Bring Back Birdie (the sequel to Bye Bye Birdie)
Love Never Dies (the sequel to The Phantom of the Opera)
The Best Little Whorehouse Goes Public (if you have to ask...)
In general, musicals have an even more dismal record as far as successful sequels than film franchises, and certainly a worse record than books. The only sequels I can think of off the top of y head that were truly successful and worthy works of art in their own right were William Finn's Falsettos musicals.
With all of that in mind, below please find David and my ideas for likely sequels to The Music Man:
Prequel: The Music Boy
Muthic Man 2: Winthrop'th Revenge
Music Man 3: Pick a Little, Kill a Little
Music Man 4: Paroot of All Evil
Music Man 5: My Fright Night
Music Man 6: Sadder but Deader Girl
Would love to hear any of your suggestions for additional music man sequels (or other unnecessary sequels to musicals) in the comments!