All done? Good.
It's hilarious. There's are several visceral reactions going on at once. You see, we are in on the prank, so we can laugh at the sales rep's expense. His exclamation such as "You are liable for any damages!" and "Sir, please take us back now!" are belly-slappers because we know who's driving the car. The sales rep is naturally freaking out because all he knows is that he's being driven around by some sort of psychopath.
But did you catch what happened at the end?
Watch those last 15 seconds or so again. Jeff reveals himself, realization dawns on the face of the sales rep, and then he says "Can we do it again?!?!?"
Once he knew who was in control, what was a horror show became a thrill ride to be experienced again.
How many times in our lives has this same dynamic played out? How many times have we stressed out because we felt out of control. Once we realize who is in control, we can actually sit back and enjoy the ride.
The LORD bless you and keep you; the LORD make his face to shine upon you and be gracious to you; the LORD lift up his countenance upon you and give you peace.
Numbers 6:24-26 (ESV)