Suggestion: A hat that enables the use of the @disguise command (which lets you change sprite to look like a monster.) Probably via fairy auction (exclusivity for a while) or hatter.
Not even sure if it's doable, but it'd be a pretty fun novelty, like the artist pencils letting you make graffiti.
it is my understanding that something was tried in the past with such @commands and it crashed the server. Least I believe that is what a gm told me when I inquired about @size1 and @size2
Characters:Captain Usopp, Tony Tony Chopper, Zarathustra, Zoroaster
It's not so much that it's undoable, but rather it has gameplay changing effects (in fact, one of the most dangerous cheat involves disguises.) When a GM disguise players, GM will also undisguise upon said players leaving the town (or GM is following said player to follow through to make sure that it does not get out of hand.)