It has been, and continues to be, one of the most successful and popular musicals of the past 15 years, even though it has never featured any headliners and most of its performers are, well, dumb.It debuted off-Broadway in 2003 and that same year moved to the Great White Way, where it remained through 2009, winning Tony Awards for best musical, score and book.It has had a great international run from Hong Kong to South …