Category: The Melancholy of Haruhi Suzumiya (all series)
Characters: Haruhi Suzumiya, Yuki Nagato, Mikuru Asahina, Kyon, Itsuki Koizumi, Tsuruya, Ryouko Asakura, Emiri Kimidori.
There are more characters, but I just don't feel like typing them all in.
Unless you're planning posting a story set in the universe, I don't see much adding a new category if it's gonna wind being unused.
I don't plan on writing a story myself (I can't write one to ave my life), but I posted a challenge for this universe. I suggested adding this category in case someone decides to write a story for it.