How We Roll Winner
Additionally, if you are unsure as to whether the creators are okay with fanfictions etc., you can just get over to Wikipedia and check out if the particular show/anime/cartoon etc. has a history of fanfictions or if the developers are okay with it. However, don't get upset if the page doesn't say so, check on Google.
As an example, there is a special mention on the "Fan-Fictions" page of Wikipedia where it says specifically that developers like CLAMP(They make anime and manga) are okay with fanfictions of their shows.
I was unsure about a similar thing so I asked Eukara Vox. You can approach(PM) her too if you want info.