This year I made what may be the world's first botanically accurate Poison Ivy  costume.
Generally, Poison Ivy costumes use English Ivy leaves, leading to a misunderstanding of the true appearance of dangerous poison ivy.

In order to make real poison ivy leaf shapes, I had to make them myself.  I used photos of Poison Ivy from my backyard to trace genuine leaf shapes. Then I used the laser cutter on wool felt to make leaves for my costume.