You could give an "online demonstration of how to use the Internet"
(or fill in you own favorite computer demo).
 
If it goes as normal, you will experience N glitches. In true irreproducible
fashion, you'll never be able to demonstrate the same N glitches again!
 
Or, should the demo go perfectly, well then --that's really special; you'll
NEVER be able to reproduce that demo again......
Peter