Twinkies are a packaged sponegcake with cream filling that are the subject of many jokes in the US. They come wrapped in cellophane and so people assume they are indestructible or will stay fresh forever. If unfamiliar with twinkies, go here to be enlightened:

Temple of Twinkie

Go here for science experiments with twinkies:
The T.W.I.N.K.I.E. project