I heard this expression in series called "Friends" and I'm not really sure what it means. Is it common to use it?
Here's the context:
Phoebe: Why are you guys so upset? It's Old Yeller, it's a happy movie.
Rachel: What?
Ross: What're you talkin' about?
Phoebe: C'mon, happy family gets a dog, frontier fun.
Ross: Yeah but Pheebs, what about the end?
Phoebe: What when Yeller saves the family from the wolf and everyone's happy?
Rachel: That's not the end.
She's suggesting that the movie depicts all the best parts of being a family living on the American frontier, all the fun they had living that way.
No, it's not a common expression.
And it's the only Disney movie I know with a very sad ending.
I'm not a teacher, but I write for a living. Please don't ask me about 2nd conditionals, but I'm a safe bet for what reads well in (American) English.