Hilton Als: "Difference is usually synonymous with danger: it’s the outsider or the outcast who introduces sex and violence into the musical’s relatively moral world. (American musicals almost always argue in favor of the status quo.)"
Scott Miller: This is also a common device in many musicals, in which the protagonist must either assimilate into the community (as in The Music Man, Brigadoon, La Cage aux Folles, Hello, Dolly!) or be removed (as in Cabaret, Sweeney Todd, Man of La Mancha, Bat Boy, Urinetown).
Stephen Sondheim: "I remember how everyone goes off to the clambake at the end of Act One and Jigger just follows, and he was the only one walking on stage as the curtain came down. I was sobbing."