Growing Wings

Not every Winged Humanoid is born that way. Sometimes, they have to go through Metamorphosis first. This can occur in any number of ways:
 * The character wakes up one morning to discover tiny wings on their back, which grow over time until they are functional.
 * The more realistic the story is, the more slow and painful the change will be. If the keeled sternum and large flight muscles also develop, it can be a mild case of Body Horror.
 * The wings appear suddenly, often as a result of a magical spell.
 * The initial sprouts can be ridges, feathery tufts, or tiny, articulated wings.

Note that this trope is for permanent or semi-permanent wings. Wings that appear and disappear go into the category of Power Gives You Wings.

Anime and Manga

 * Princess Ai sprouts a pair, on account of her unconventional heritage.

Literature

 * In one of the later Wild Cards books, Peregrine recounts how she grew wings after starting puberty. The comic book adaptation actually shows us the moment when her pediatrician first figures out what's happening and tells her.

Music Video

 * The Music Video for Asian Kung Fu Generation's "After Dark" features a man randomly sprouting wings on his back one day, and desperately hiding them until a window-washer is dangerously close to falling off a building. Awesomeness ensues.