The boss is hosting a costume contest at work, and there's a big cash prize for the winner!
his costume on the day 
of the Halloween party"?
زيه في يوم حفل الهالوين"؟
su disfraz
el día de la fiesta de Halloween?
il suo costume il giorno della festa di Halloween"?
который забыл свой костюм на вечеринку?