Buy 20 different brands of chocolate bars (snickers, baby ruth, milky way, twix etc.) and put a sizeable piece of each on a paper plate, but not the whole bar - just a piece of each. Number each plate with a marker from 1 to 20 and make sure that you keep track of which candy bar is put on each numbered plate. Make a list such as #1 Snickers #2 Mr. Goodbar #3 Kitkat etc. Put each plate in the microwave and wait until the candy bar is melted pretty good. Some will melt better than others, therefore you may have to do some squashing with your finger to make them a bit less recognizable. But don't melt them or squash them too much since it may make them completely unrecognizable. You want to give your guests a fighting chance here. Next, after all melting and squashing is complete, put all the plates on a table with paper and pencils and have them write down their guesses. Then read off the answers and have them mark their correct guesses. The one with the most correct wins. What do they win? Candy bars of course!