Zainab  Al-Alwani, Instructor of Fiqh and Islamic Studies, Graduate School of Islamic and Social Sciences, states: “What is more important is to ask about the purpose and the content of these parties. If they are parties where haram (forbidden) acts are committed such as drinking, free mixing, etc. then the question of the dress and wig is no longer applicable and you must avoid these parties.
However, if no haram acts will be committed, then there is nothing wrong with wearing fancy dress that do not reveal the ’Awrah. Wearing wig is also allowed in this case, as it is part of costume and there is no deception intended. However, I would suggest that other things be chosen since there are so many alternatives nowadays.”