Mine just had to take 100 pieces of a snack. I found out the night before (as always) and sent her with sunflower seed kernels because that's all I could find in the pantry. She counted them 4 times because she didn't believe 100 of anything could look so small
I hate dress up days, it's a pain with 4 girls, but I always let them participate.
I can't think of anything for looking 100, other than a cane and glasses, but the cane could definitely cause problems for the teacher.