How to get the Sack in 20 Days
Day 1: Use clear tape on the bottom of all the mouses, so they don't work. If they are those snazzy light ones, use a small postage sticker
Day 2: Swap all the keys around, on all the keyboards
Day 3: Swap the mouse/keyboards around, where they are plugged in
Day 4: take screenshots of everyone's desktop, then set the pic as wallpaper, and hide all the icons/task bar.
Day 5: Change the language on all the computers from English to American
Day 6: Make internal prank-phone calls all day
Day 7: Get the client list, sign them all up to the popbitch news letter.
Day 8: Change the auto-correct list on word so that common words like "the" come out as "cockbadger"
Day 9: unscrew the bottom of everyone's chairs.
Day 10: put little holes in all the coffee/water cups
Day 11: superglue a one-pound to the floor, in a really inconvient place (like a walkway, or lift-enterance)
Day 12: Make a porno-picture of the boss... email to everyone in office, print out for the cleaners.
Day 13: eat something like an Omlette for lunch at your desk, put in bag, leave bag in someone else's desk, but hidden away.
Day 14: Get everyone to come out for a pub lunch, get them all considerably drunk.
Day 15: Take out all the mouse-balls, replace with a round boiled sweet.
Day 16: Set off the fire-alarm.
Day 17: Steal all the smoker's lighters.
Day 18: Do nothing at all... paranoia
Day 19: days 1 - 18 replace coffee in office coffee machine with decaff, day 19, switch back to full-caffeine coffee
Day 20: Tell the boss to play along... tell everyone else that you're not really leaving, and it was just a prank.