If a "guilty pleasure" can include a popular musical that is a shallow piece of fluff, then it's definitely "Something Rotten. "
If it can only be a not-well-reviewed or not popular musical, I'd go with the 2004 movie version of "The Phantom of the Opera. " I still think Gerard Butler is one of the best Phantoms in terms of his acting, and his singing is a whole lot better than Russell Crowe 's. In fact, if they wanted an a-list Javert instead of a singer, they should have gone with Gerard Butler.
Audrey, the Phantom Phanatic, who nonetheless would rather be Jean Valjean, who knew how to make lemonade out of lemons.