thou hast a daughter? how old, if I may ask?
ha ha, Harry Potter probably has the biggest fan following of anything in existence, including Star Trek, Lord of the Rings, and Twilight. Only Star Wars, I think, may possibly have more, and then just because it's so generation-spanning... but the Star Wars people don't make as much fanart/fanfiction as the kiddies do for HP. I myself have managed to avoid doing any Harry Pooter fan stuff, but... few have. Though I have done fanfics for Star Wars and LotR... sigh.
I guess by the strictest definition an OC really shouldn't be for a fanfic, but I dunno.
ANYHOW. Long response.