At the end of The Music Man, when Harold Hill is being forced to face the consequences of his actions, several boys with instruments show up, which "proves" he was legitimate all along.

It's been years since I've seen the movie. Where do those instruments come from? Who arranged for the boys to show up with them? Who taught them to play "76 Trombones" (albeit badly)? I was telling the spousal unit about the movie and when I got to the part about the instruments showing up she railed against the ridiculosity of it all, saying she could never take seriously a movie with such a Deux Ex Machina ending.