an 'ugly duckling' that has become a beautiful swan [=an ugly/unsuccessful person or thing that has become beautiful/successful]
('informal') That dog of yours is '(as) ugly as sin'. [=very ugly]
The house is an 'ugly duckling', but it has a lot of potential.
(..) Mom. Not cool. And here, he's all dressed up in his Sunday best. He looks like a girl! Yes, he does. An ugly girl! You're funny! Yes! Mine's shaped like a dead guy! Mr. Perkins, your son is here. Send him in. Hey, Dad. (..)2010 Despicable Me