Warning: I am not in any way shape or form responsible if you take this prank to the next level or modify it to become harmful in any way.
Automobile parts(spare pistons, srews, nuts, bolts, gears, ecta etca)
Car jacks x2
Hydraulic car lift
Access to victims hood
Step 1: Lift
Use the car lift to lift up the victims car just enough to slide in the car jacks and set them up. Dont worry were not taking apart there car so bear with me.
Step 2: Hood
Step 3: All Finished
Eventually they will go around to the back and discover they have been pranked but you have the car lift out of sight so all you need to do is get the car down off the jacks and be on your way. Its best to do this prank on flat as possible ground, because they will try to go at first then realize that Theres a problem.