The Ugly Duckling

The Ugly Duckling is a classic-contemporary story by Hans Christian Andersen about a duckling, notably uglier than and different-looking from the other ducklings in its brood, who grows up to be a swan. It is often considered a metaphor for the experience of an awkward stage in a child's growth.

This is also often used as a metaphor for anything neglected continually, or anything neglected at first, then becoming popular.