Harry Potter and the Glorious Puberty
Adam Rifkin stashed this in Aging
that turned out to be a very good looking cast! even the clumsy kid (can't think of his name now) turned out to be an armani model!?!
Matt Lewis as Neville Longbottom!
In fairness, no one saw that coming.
He's the most remarkable of the transformations above.
But as you said, they all did well.