Boo! What could possibly be scarier than mathematical objects to your math students? Here are some of scary math objects you can dress up as for upcoming Halloween (or just any time you want to spook your students or colleagues!)
For calculus students:
Integrals - invite couple of your friends to join and walk around together so you are a "triple integral"
Differentials - dx, dy, dr, dθ, etc... choose your favorite. Have others join and make different combinations to make different coordinate combo
Draw on your shirt two lines crossing each other. Attach an object with interesting shape on the crossing point - Tangent plane
For general math department:
White top & yellow bottom and some number on your back in black - Graduate Text of Mathematics