A person who has grown up as an physically unattractive person but later becomes good looking. As a young person they were able to develope a non-bitch attitude and were able to have some developement in their brain. Thus they get a very likeable personality because they can't rely on their looks.
When they became attractive they have a great personality unlike people who grew up knowing that they are better looking than other people.
Hence Ugly duckling Syndrome
Guy 1: Man that hot chick i was with last night was so funny and smart