Two people need to do this prank.
First, you need a car. Where the steering wheel is, take it off and put it on the passenger side, so that the peddles remain in the driver side and the wheel in the passenger side. Take it to a garage perhaps on the back of a truck or if you're really clever, drive it up with the passenger steering and the driver working the peddles! I know in London the guys in the garage offer to drive the car in for you so both the people get out the car and let the garage guy jump in and watch his face as he looks well and truly confused! Then perhaps something can be put in the glove box, seen as poo seems to be such a trend, the driver can suggest that the garage man can unscrew the steering wheel with the screw driver in the glove box. Then when he opens it, he'll get a nasty suprise, or maybe stick a snake in there, or a really pissed off raccoon. Either works!