This type of thing is right up my alley. As for ideas, maybe an edible chunk of uranium, or some chalk candy.

A pumpkin dish is a no-brainer. I had a muffin earlier, and this just gave me a hankering for some pumpkin muffins. A fun tagline for them could be "Serve a platter of these to your guests, and soon they'll be saying 'what pumpkin muffins?'" (imagine crumbs around their mouths)