If you're gonna advertise a "short" before a movie, it needs to be at least one of two things:
1. Short
2. Really, really good.
#2 is debatable. I thought it was bad, and I'm a "Frozen" fan. But other people love it, so it's whatever.
But it was really, really long. When I think of a "short", I'm thinking 7-10 minutes, tops. But 21 minutes? AFTER the previews? All the kids around me were squirming. Very little laughter in the theater. AGAIN, I know that's purely subjective. Your experience was different. But if it's not gonna be great, it at least needs to be short. And it wasn't.
Again, I really loved "Frozen". Still do. But this was just way too much, and mis-advertised. It should have been an ABC prime-time special(which would've been a ratings bonanza)....not a "short" before a full-length feature film.