Example: Reading about an entire series on Wikipedia then doing a fic based on what you read or being inspired by promo stills from a movie or anime.

Idk if this counts but I used the plot of a fandom I've never watched to write one for a fandom that I did. I've also done fics based on single spoiler images from a new season of a show I like.

That counts. That's actually along the idea of what I was saying. Good example :)

If I were to write a fic for a fandom I'm not familiar with I don't think it would be very good.

Thanks :D

I'd be enough of a fan to have watched or read what the fandom is about before I'd be enough of a fan to write about it. I also think you could misinterpret something more easily if you were just going from wiki entries etc.

^True, wiki has been known to be unreliable sometimes. I think it's because you can edit the article or something?

^Anyone can edit it, and sometimes biased fans alter the articles to reflect their own opinions on characters and so on.

^Yeah, that's gotten them into trouble before, too.