@Fun: As for the 'Tell them the stove is cold when it is on (being stupid; they will touch it)' thing. I have actually done that before. Touch a stove when it's on, I mean. xD
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Kill their pets.
While they are watching a kid show, change it to the news.
Kill them.
Kill their relatives.
Kill their friends.
Torture them.
Lock them outside at night.
Lock them in the garage.
Ditch them.
Yell at them.
Bite them.
Break their leg.
Break their face.
Break their arm.
Slap them.
Pour curry powder in their eyes.... Yusssss...
Dunk them in a swimming pool.
When they have to use the bathroom, lock the door to it so they can't get in. When they finally have a 'accident' take them outside and call their friends over. It works. xD Oh, but make sure to point out that they did so. Heee hee.
When they have to use the bathroom, go "Drip, drop, drip, drop~" Over and over, blocking the door to the bathrooom while doing so. xDD
Approach them with a knife, looking all murderous. (don't actually kill them or hurt them. :P) Then laugh at them when they cry.