The costume person (mainly a US English term) or the fancy dress person (a supplementary commons British or Commonwealth English term), mainly around coeval Western culture is a type of party where guests dress up inside the costume. Which are actually especially popular in the United States around Halloween, when teenagers and adults who can be considered as well old for trick-or-treating attend a costume person instead. Such parties come too popular when you took a Carnival season, such as at Mardi Gras.