Awesome Ride Prank

I can imagine that an amusement park ride operator's job would probably get a bit boring towards the end of the day.  So why not mix things up a bit, and play a [safe] prank on an unsuspecting rider?  Maybe say something along the lines of "the harness isn't working" right before launching his ride?  The reaction is priceless, and I'm surprised he didn't s*it his pants.