First R-Rated Musical

I think "Pop"sical would be closer!

Just to muddy your waters a little further - Characters sing some of their lines = Musical (Magic Flute, Carmen, Wozzeck) ?!?

Style has to come into it somewhere along the line…

People break out in song and/or dance in public, and anonymous passersby join in-musical.
People break out in song and/or dance in public, someone gets hit by a truck, the police are called, and anonymous passersby yell “Shut the fuck up!”-not a musical.

There actually *was *a musical of “Saturday Night Fever” that played on Broadway from 1999-2000. That version has not yet been turned into a movie and the original film is clearly not a musical.