It's never a good strategy to start off the valet transaction in a negative way.
Some people don't realize that valets aren't peons. When they have control of your vehicle, that's power. They can do whatever they want to it. And it can be outrageous.
If you mistreat a valet worker, there's a good chance they will be inclined to get some satisfaction. They have a vast array of creative payback options to choose from.
Remember, you're dealing with young people. And they are totally wired for mischief. You don't want to trigger a payback reaction.
In this comedic valet episode, the valet dishes out revenge by doing several things. One of them includes emptying out the customer's windshield washer fluid. That's fairly low on the severity scale of what can be done.
A more likely result from valet mistreatment:
Rough driving. This includes stomping on the gas peddle, heavy braking, hard cornering, over-revving of the engine, drifting attempts, burnouts, locking up the emergency brake while the car is moving forward, and going for the speed record inside the garage.
Intentional infliction of mechanical damage. This includes things like "neutral drops," which involves revving the engine high in neutral and then slamming it into drive, plus there's also... stopping the car by putting it into park while the vehicle is moving, and burning up the clutch.
Intentional infliction of cosmetic damage. They could easily give your car a new scratch by rubbing a key against the paint. They could open a car door into it, dinging the body. They could grind a wheel against a curb, or back it into a concrete column. Or grind the air-dam on to a curb.
Degradation in the quality of your valet parking experience. It could take a long time for your car to be brought out. They might just happen to lose your key. Things like that.
Other sneaky revenge tactics:
A valet might stick his hand down his butt crack, or rub his sweaty balls, and then rub that hand all over your steering wheel.
A valet might decide to fart in your car just before he gets out and hands you the keys.
Your radio station presets might be different when you get the car back.
Your seat and mirrors could all be moved, maybe the steering wheel position too.
A booger might get smeared on to your power window button.
The air pressure in your tires might suddenly be substantially lower, or maybe a tire might go flat completely.
Of course, things might disappear from the car too.
If you mistreat the valet, especially in an egregious way, you're being dumb.
It's a BIG MISTAKE.
By the way... regarding burnouts, it could turn out like this...