The admins discussed this a few days ago, but I just added a guideline in the Omnitrix Alien layout that states that users are not to add 'Category:Heroes' or 'Category:Villains' to alien pages, as the alien itself is not a hero/villain, the wearer of the Omnitrix is. Also, just a reminder, do not add gender categories to Omnitrix alien pages. This has been a 'rule' for years, yet some people still disobey it. Thanks for reading this minor update, please keep this message in mind.
I'd advise not taking advantage of the loophole. Anyway, I only reopened this thread to say that these changes have been added to the official rules. Users can and will be warned should they go against the rule.