You’ll sweep up in the best costume category when you enter as Mary Poppins and Bert. (sorry, the pun had to be made)
Mary needs a white blouse, navy skirt, peacoat, boots, a red bowtie, a hat and, of course, her very important accessories: an umbrella and carpet bag.
Chimney sweep Bert needs dark pants and a dark jacket, a red scarf, a newsboy-style hat, and his own very important accessory: a broom. Add black makeup for soot and spit-spot, off you go.