Prescott Programming Librarian, Becky Arenivar, shared some great ideas for a Grossology Program she held. By far the grossest thing they did was bobbing for Spam (yecccchh!):

Our Grossology event included 3 food challenges, 3 touching challenges and the kids got to make blood and vomit to take home!

There are recipes all over the Internet for Kitty Litter Cake, which looks very real and actually tastes good! We served it with a (new) litter scoop, and mixed it up in a (new) litter box. We also offered Edible Vomit to eat. Our 3rd food challenge was Bobbing for Spam!

Our touching challenges (behind a black piece of fabric, so kids couldn’t see, were Slimy Brains, Bloody Heart and Gooey Eyeballs. The recipes for Edible Vomit and Blood were out of 100% Pure Fake by Lyn Thomas, Kids Can Press, 2009.
Most kids did the 2 eating challenges and the 3 touching challenges, but we had only 4 takers for the Bobbing for Spam. It even smelled gross. The Spam sinks to the bottom, so you really have to go after it.

We gave kids medals (cardboard, spray painted gold or silver, with a label identifying the challenge) for each challenge they did. It was fun to see them walk out wearing multiple medals!