I rarely play pranks. But a long time ago, a cow orker twitted me for reheating garlic soup in the office microwave and "stinking up the place." So when my housemate was making Christmas cookies a week or so later, I begged a little dough and decorated a few cookies with garlic.

At lunch the next day I ate my delicious cookies and offered said cow orker one. I handed him a garlic cookie and he stuck it in his mouth without looking. Then his eyes widened and he yelled, "GARLIC!?!" It was quite gratifying.

(And then our Chinese cow orker asked me if he could have one of the garlic ones, too. He quite liked them, he said!)