If you distill Cookie Monster down to his component parts, this is basically what you get: sweetness, cookies, blue, and whimsy.
considering how kids never really just pick up a sandwich and eat it like normal human beings, you can make them lunches that defy the norms of sandwich making for fun. They're going to decimate the thing anyway, why not get them excited about the beauty they are about to destroy?
When I was a kid my mom had a cookbook all about how to make creative cakes with nothing but a round cake pan, a bundt pan and a square pan. She made caterpillars and castles and Snoopy and all sorts of amazing creations but I don't think I ever saw a donut. It's so simple it just slipped under the radar.