Mr Burns: Better yet, I'll make you my.. Prank monkey!
Alas, I've never devised a master prank by myself, I tend to make an ass of myself, not others

There was one hilarious prank I joined in on during our year 7 school camping trip thing, though. There was this real fat bastard in our year, and he decided to make it a habit of his to steal food supplies before people could get a chance to cook them for dinner. The guy would actually sneak off with blocks of compound chocolate! Or bags of raw sausages!
We didn't wanna guess if he ate them or not, we'd guessed he'd just toss them in the river or something. I'm sure it must of been amusing.
Anyway, last night of camp, a bunch of us waited till about 2 AM, when he was asleep in his tent. It was three to a tent, but his 'tent buddies' had gotten in on our act.
Keep in mind, he was a damn heavy sleeper. You could set off an fire cracker next to his face and he'd still sleep.
We snuck in, and coated him with whipped cream. We used two whole cans. Eventually, he looked like the mashmellow man from Ghostbusters. It would of been better if he was in his sleeping bag.. But, oh well.
We then proceeded to drag his tent, with him in it of course, onto an angry ants nest. We'd scuffed it up and got them all pissed off, it was an army.
We then ran away, hid behind some trees and giggled like school girls. Within seconds the mashmellow man lept up, bashing his head on the tent pole, tumbled over, and burst out of the front, running and screaming like a baby. Ants had covered his goo like coating, and had flooded the tent.
It was hilarious.
We got in massive trouble the next day, but it was allll worth it.