The Ugly Duckling is the character from the Hans Christian Andersen fairy tale of the same name. His own family of ducklings reject him because he looks different. The moral of the story is sometimes true beauty will appear sooner in time.
In the original story
The Ugly Duckling was rejected by his own family of ducklings because he looked different. He came to an old woman's house, but her cat and hen teased him mercilessly, so he ran away. He later saw a group of swans migrating, so he wanted to join them, but he couldn't because he could not fly since he was too young. Winter arrives, and a farmer finds and carries the freezing little duckling home, but the foundling is frightened by the farmer’s noisy children and flees the house. He spends a miserable winter alone in the outdoors, mostly hiding in a cave on the lake that partly freezes over. When spring arrives a flock of swans descends on the now thawing lake. The Ugly Duckling, now fully grown and matured, decides to throw himself at the flock of swans deciding that it is better to be killed by such beautiful birds than to live a life of ugliness and misery. He is shocked when the swans welcome and accept him, only to realize by looking at his reflection in the water that he has grown into one of them. The flock take flight to the air, and the now beautiful swan spreads his gorgeous large wings and takes flight with the rest of his new kind family.
The Ugly Duckling (1931)
In this version, the Ugly Duckling is actually a duck whose egg somehow found its way into a chicken's nest rather than a swan raised by ducks. Though initially rejected by his hen mother for being of a different species, the Ugly Duckling is able to earn his family's acceptance when he risks his own life to save his foster siblings from drowning.
The Ugly Duckling (1939)
In this version, like his original counterpart, the Ugly Duckling is a cygnet (a baby swan) whose egg somehow found its way into the ducks' nest. He was initally oblivious to his foster family's rejection by following the Mother Duck when she went to swim with her ducklings until she suddenly snapped at him to go away before turning her back to him along with her ducklings.
Confused, the Ugly Duckling, who wonders why she doesn't like him, looks at the pond, and (following his initial fright) is shocked to see how different from the other ducklings he is; especially when he sees how happy they are without him around. Realizing he has no place with them, he wanders away and eventually comes across a nest of sparrow chicks in an overhead branch. Deciding that they would become his new family, the Ugly Duckling climbs into the nest but is violently chased off by the mother when he eats a worm intended for her own babies. While fleeing her attack, he retreats back into the pond where he encounters a wooden duck decoy. When it doesn't scold him or try to drive him off, he interprets its silence as acceptance and adopts it as his new mother. Unfortunately, while playing on and around his new "parent," the Ugly Duckling causes it to tip over and knock him on the head with its bill.
Shocked by the sudden and unprovoked attack, the Ugly Duckling escapes to the safety of the bank where he watches the decoy turn its back on him just like the Mother Duck. Deciding he is too ugly to be loved, the Ugly Duckling gives up hope of ever finding a family and breaks down in tears. As he sobs, the Ugly Duckling is approached by a group of cygnets who to his surprise not only look like him but actually seem happy to see him. Encouraged by their own honks, he stops crying and dives in to play with them until the cygnets' beautiful mother calls them to her side. Expecting her to reject him for his ugliness like all the rest, the Ugly Duckling decides to paddle away when the Mother Swan suddenly swims up and reaches for him. Certain that she was going to attack him, he briefly cowers in fear until she pulls him close and lovingly embraces him as one of her own whereupon he realizes to his joy who he really is and where he belongs.
No longer an Ugly Duckling, the Little Swan swims home along with the others when he's spotted by none other than the ducks. The Mother Duck invites him to return to them but the Little Swan realizes she only wants him now because of what he has the potential to become, and decides to remain with his true mother and siblings instead; turning his back on the ducks as he follows the swans into the distance.