lucky duckling

lucky break

A stroke of luck; a fortunate event, particularly of the sort that propels one to success, fame, etc.

lucky dip

A selection solely at random.

lucky dog

Someone with astounding good luck.

lucky star

Something that appears to give a person luck

strike it lucky

To have unexpected good fortune.

thank one's lucky stars

To be grateful, feel oneself fortunate, consider oneself lucky (especially in avoiding some calamity).

ugly duckling

A young person who is ugly, but who is expected to become beautiful or handsome as they mature.