Before watching the movie:
I stumbled across this maybe decades ago, I believe referenced in an educational book about movie making, which noted that there was a movie that cast all child actors in grown-up roles, requiring all of the sets and props to be custom-built at a child scale. That obviously stuck in my mind, but I never followed up on it. Recently I watched a movie that made an offhand reference to this movie, finally looked it up, and here it is.
I had no idea before I looked it up that it was a musical. This sounds fantastic. A G-rated gangster movie musical with a completely child cast, starring Jodie Foster and Scott Baio. I mean, it could go horribly wrong, but what reputation I’ve been able to glean about it suggests not.