Fill the sugar jar with salt.
Put a whoopie cushion under your boss' chair, and a fresh fish in his desk drawer until a pile of documents.
Paint a mural in the staff room of a penis and balls.
Write on the stalls that so-and-so is in lurrrrrveeee with so-and-so.
Unplug your tech-backward colleague's monitor. When he comes to ask for help, go check and ask him why he's been porn-surfing.
Wear pantyhose and heels tomorrow and go into work.
Wear a purple shimmery wig with the above outfit.