I haven't written any fan fiction in ten years, but when I did write it, I didn't include any original characters with big roles. I prefer to use the really obscure ones in new ways. The anime I did make a fan fiction was Slayers Justice!.
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Edit: Hmm, upon further review, I suppose Talone might have been an OC, seeing that he was created as someone to interact with Sylpheel. But Amelia was the center of the fic and both Sylpheel and Talone were only in the first chapter before Amelia parted with the rest of the gang and went back to Saillune.