1. Pumpkin "pi"
Take an orange sweatshirt and use a permanent marker to draw a big "∏" <—(pi sign) on it. Draw the outline of a pumpkin around the pi. UPDATE: Amazon sellers have done the work for you!
2. An imaginary number
Dress in all black. When people ask why you are dressed that way, tell them that they can't see your actual costume because it is an imaginary number.
3. A sentence fragment
Find a skeleton outfit and, using the same permanent marker your friend used to draw the pi, draw a bunch of jagged lines in the bones, signifying breaks in structure! Bonus points if, as you talk with people, your sentences lack a subject, predicate, or complete thought!
4. A square root
Put on a sweatshirt, any sweatshirt. Use duct tape to affix 4 root vegetables (I like carrots because they are orange, but feel free to take some liberty here) in the shape of a square.
5. A book
You already have a spine and are filled with words! Wear whatever you want! (Though, a skeleton t-shirt might come in handy for illustrative purposes.)
6. Parallel lines
Find a friend and stand next to each other all night.
7. A bubble sheet
Take a sheet and wrap it around yourself (wearing clothes underneath, of course). Then, tape bubble wrap on top of the sheet. Consider carrying around bubble gum, or liquid bubbles all night. So fun!
8. A remainder
Dig up last year's costume. Wear part of it, ie: the remainder.
9. A part-of-speech
Find a speech that you like, and write the beginning onto a plain white t-shirt.
10. A logarithm
Find a stick and hit it against a table. Making... a logarithm.
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