All you need:
A Family member or a friend.
Step 1: Instant weight gain/loss!
Find the click-wheel thing on the side of the scale, thats where the one on mine was, so i don't know if other's have it. Electronic ones probably wont. Move the wheel to make the scale off balance: the second picture below is when noone is on the scale. when someone steps onto it, they seem 40 pounds heavier. Try it! It's hilarious, just don't be mean because weight is a touchy matter for some people.