Tropes! Tropes I tells ya! They're EVERYWHERE!

Tropes are those key symbols and key scenarios that have become the currency of popular culture astorytelling and media.  The ugly duckling who grows into a swan, the underdog who wins the big game, the hooker with the heart of gold, the crabby old man who learns to be happy, the "very special" episode of whatever show where they talk about something heavy and serious- these recurring themes are called TROPES. 

Here's an interesting wiki about them that gives examples and background in exhaustive detail.

http://tvtropes.org/pmwiki/pmwiki.php/Main/HomePage