Superglue has so many uses! [img]tongue.gif[/img]
Cerek, with reference to the exlax - I was going to suggest exlax brownies, leave them at the coffee pot compliments of "C".
Then there's the usual shoe polish on the black phone receiver.
Virii are also fun, if you can get some of the "joke" ones and infect her PC. (Make sure the virus scanner is disabled first. [img]tongue.gif[/img] )
Let's not forget the (in)famous milk-in-the-carpet-of-her-car trick, either. (Stinks to high heaven when the sun hits)