Some movies make sense to transform into musicals.
The Producers was a musical that was based on a movie about making a musical. So, that makes sense. Don't forget they also made a movie based on the musical based on a movie about making a musical.
Wicked is based on a prequel to The Wizard of Oz. We've all seen the movie, singing, dancing, fa la la 'ing. (The Youtube link up there is the Tony performance of Defying Gravity - amazing)
The Wedding Singer. Ok, it was filled with great 80s music and features a main character that makes his living SINGING!
Footloose. A movie all about dancing, so a Broadway show all about dancing!
But... now playing ... LEGALLY BLONDE THE MUSICAL. Umm, I don't remember much about the movie, but I don't remember Reese running around singing and dancing through it. Do you?