To me there is nothing more enjoyable than a GOOD practical joke. A good one involves no one getting hurt and everybody gets a laugh.
My very good friend Tom and I grew up together and stayed in touch at least monthly. He shows up at the shop every once in a while with two things in his hand that used to be one thing. I drop whatever I'm doing and wave the wand. He, in turn, has done mucho favors for me.
A few years ago, Tom bought a new S-10 pick-up that he waited for months. God, he LOVED that truck from the get-go. So, I would stop at his apartment complex every night and add 2 gallons of gas to his tank. Now he REALLY, REALLY loves that truck, after all, he's getting 50 miles to the gallon and he's telling everybody. I did this for a month then stopped. He's heartbroken and takes it back to the dealer that he bought it from and where he used to be a salesman. He complains the his mileage is now down to 22 mpg from 50. The service rep looks at him like he's from another planet. I never told him 'cuz I hope I can get him again.
Any other good ideas?