Stick to the Script
When you give a scripted demonstration of an early version prototype, don't improvise. If you try something different, who knows what might happen?
When I was about to give the first demonstration of a Minnesota tax software prototype, one of the database developers claimed there was nothing I could do to hurt the database. I foolishly believed him and used the prototype to view some data that was not part of my demonstration script. That crashed the database and it took almost three hours for the developers to put things back together.
Fortunately I made this mistake early in the day when the customers and I had a couple hours of design discussions to work through before the demonstration. The prototype was working again just when we needed it but it was a very close call.