Well, since no one else has told any other practical joke stories, I'll start with the first one that comes to my mind.
So, as mighty fine fourteen year olds, Dilmah and co. spent a summer's day walking around suburban Perth, wreaking havoc and cleaning several McDonalds outlets of their triple cheeseburger patties as well as frequenting the local cinema.
After retreating to the house of a mate living close by, about half a dozen of us got the okay from our folks to spend the night there, playing Halo to loud hip hop whilst consuming the contents of the host's fridge. After the majority of them had decided to doze off at around three in the morning after an epic game of CS, a mate and I checked the host was fast asleep before raiding his bathroom and returning with toothpaste, a bar of soap and a cup of water.
As my mate squirted toothpaste carefully into the host's right hand, I used the bar of soap and cup of water to moisten the wooden floorboards next to the couch he was sleeping on. Giggling with anticipation, we turned on the lights to see him work his newest tube of colgate all over the left side of his face and through his hair. Realising that something was amiss, he attempted to open his eyes whilst placing a foot on the ground, only to slip forwards as he stepped out and fall face first onto the back of another mate of ours who was dozing off on the carpet.
lulz were had.
We also ran very, very, fast down his stairs.