Normal paper bag right? WRONG! Lift this up and your prankee should get a nice surprise. This is easy but hilarious to watch. So lets jump right in
Step 1: You Will Need
A sandwich bag
A handful of Lego or other small things
Step 2: Cut a Hole in the Paper Bag
Step 3: Setting Up
Put your bag in someplace curious bystanders will notice it now fill the bag with the items of your choice. They should fit through the hole in the bottom.
Step 4: Watch It Unfold
Sit somewhere and get some popcorn.
My experience with thus is that sometimes people will actually fix it after the initial shock of getting a bunch of stuff falling out of the bottom of the bag. It worked so well for me I was able to trick my whole family before even getting up.
Step 5: Vote!
If you enjoyed this instructable (or the results of it) please vote for it in the April fool's contest. Thanks, and keep making stuff.