(last updated: 10/08/16)
The administration of MotM supports creativity and exploration in themeliness, and strongly believes one novel character idea is much better than forty that simply 'fit the mold of what's considered acceptable.' That said, the administration also has a duty to its playerbase to assure that disruptive designs and concepts do not make it onto the game, and that individual player concepting is protected.
Typically, what you will find here are concepts that are either banned, or meant to be rare enough that only one or two players will have them. Administration will periodically review this list and remove or add items as appropriate.
Characters that hail from alternate dimensions
Despite the existence of Mortal Kombat in theme, there is no such thing as an alternate dimension on MotM. See the Metanatural file for more information.
Aliens, Characters of Different Species
Many characters from series titles selected for inclusion on MotM were barred from entry into the theme because they were from off world. All characters on MotM originated on this world, as a human, no matter what form they may have now. Sorry, Mars People, you're out.
Your character must remain relatively sane. While it's okay to play a serial killer, succubus, transvestite or former stripper due to the nature of the themes MotM actually supports, the line is drawn when the element becomes the concept. Rapists, child molesters, sex addicts,people-butchers, extreme racists, etc. typically cause more grief than they add to the playing field, and so are banned.
Keep in mind that a new character application may cause an element to be added to this list--it is not meant to be 'all inclusive' of designs that may be sent back for theme or taste reasons.