Hydra

Wearing the large suit was deceptive. She was *supposed* to look like a monster, wearing it. But it was, and still is, just a skin-tight leathery suit with claws, tail, and two fake heads. She left it unzipped just an inch in the front. As the night wore on, her body changed under the suit, bulging outwards and connecting new tissues. She enjoyed strutting around the party, the looks from the other costumed people growing more and more disturbed. "Did she always have claws like that?" "No...

Unfortunately, they quickly found out that none of the heads spoke the others' language and, indeed, even desired to eat each other, which was thoroughly unpleasant.