I was helping a friend of mine who owned a driving school years ago, and I was taking kids out and teaching them how to drive. I would teach them parallel parking in front of an elementary school on the weekends, and we would put out cones and the kids would try to park between them.
We were doing this one weekend and two Maryland State Police troopers were running a speed trap across from the school, and when they weren't writing tickets they were laughing their asses off at the kids running up on the curb, hitting the cones, etc. When it looked like the Troopers were getting ready to move on, I called over to them and challenged them to come on over and show the kids how it's done.
They jumped into their Crown Vic, came over to the school, and said they would be glad to show how they do it. As they went around the parking lot to get into position, I had two of the kids kick the cones about two feet closer together. The first guy got in but did a crappy job, so of course his pal has to show him up.

They switched seats and when they went to swing around I had the kids move the cones in another foot or so. The second trooper got the car in, but it was worse than the first guy, who was now desperate to try again so he wouldn't look like a failure in front of a bunch of teenagers.
Once again, I had the kids bump the cones in, and neither guy could park the car, which was when we all started laughing and the cops finally figured out they had been had and left.

I saw the same two guys a few weeks later in the same spot and asked them if they wanted to try again, but they weren't gonna get fooled twice.
