Maybe something about the screen, color and sound? an 8 year's experience with computers is pretty much limited to games and visuals. Being able to do arithmetic is not impressive to them, they know how to add already! I think the idea that "computers are dumb, but very fast" is a good theme, maybe some kind of counting competition between your program and the kids? Kids are also puzzled by the fact that "those nice pictures are stored somewhere in China, and when I click on this mouse, it travls millions of miles, through this phone line, and come to this screen", maybe show them them the binary file of a gif image, and explain how that somehow produces that nice picture on the screen?
in reply to How to introduce 8 year olds to (Perl) programming?