Looking for the Letter M? That themed party will be so much fun once you've found the perfect outfit! We've got costumes from films, tv, games and more in this category. Shop Mens Mario costumes and Womens Marilyn Monroe outfits. Think World Book Day with this Mary Poppins costume, which even includes the Parrot Umbrella cover! Your kids can look cool in Minion costumes, available for boys and girls and officially licensed by Universal Studios. Shopping the alphabet is easy with the Letter M. You can be a mermaid or mummy, Mad Hatter or monkey, and you'll be ready to boogy the night away in no time! Last minute delivery options available.