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.
(..) I am a man! He's a man! We're men! Okay, okay! Tell me how you're feeling? I feel delicate. And... annoyed... And... I think I'm ugly. That's her! This is ridiculous! I've never heard anything so... bizarre in my life! Oh stop shouting at her! (..)2006 TvShow: The IT Crowd Title: Aunt Irma Visits Season: 1 Episode 6