Holy Sister Nun Costume - Calgary, Alberta. This Nun costume is great for Halloween, theme parties, and plays like Sister Act. Say your rosary in this Mother Superior Nun costume. The Nun costume is three pieces. The dress is a simple black nylon that pulls over the head and ties behind the neck. Secondly is a white nylon like collar that drapes over the shoulders and ties behind the neck. Lastly is a nylon like headpiece with a white strip that ties the scarf.