Just Put You Username together with your favorite Pokemon, like I did!
CaptainSpicyClouds
+
Pikachu
=
Captain Pikachu
(And there you have it)
...But that doesn''t help much with ideas beyond making up a name for a Pokemon character.... and I fear this could be problematic for Rhyhorn. If the fav. Pokemon is the same as the username... a character called Rhyhorn Rhyhorn? Maybe in a comedy fic, but... =P
Basically what Feign said, and I'd place emphasis on the 'read other people's fics' part as well. That'll give you a good idea on what makes a good story, and prehaps what type of setting and/or genre appeals to you, something you'll want to write with. Consider what 'canon' you want to work from, such as anime canon, game canon, etc - or maybe something separate from them. From there you could brainstorm some, just go crazy with ideas and see what comes out of that. Good luck with it.