It was "Crazy Hair Day" at school a few weeks ago, and I remembered this cute story we did at Martha Stewart Kids with a beehive (which seemed appropriate for Bee!). I know some schools don't allow costumes on Halloween, but maybe you can get away with some fun hair?
The hair gets divided into 5 ponytails and braided with yellow yarn. (I found this video tutorial very helpful). One tip: Don't skimp on the yarn, it says you need 50 pieces, but I got tired of cutting and only used about 30. As a result Bee's beehive was not as tall as it should have been, the yarn is adding color but also volume to the hair.
Then you pile the braids on top of each other to form the beehive, securing them in place with bobby pins. (a LOT of bobby pins!)
Add some paper bees attached to pipe cleaners (or make your bees out of pom poms if you happen to have some around) and you'll all set. The whole thing took about 20 minutes from start to finish, and made Bee a very happy kindergartener.