[McMock]

Get a mate you know at a bloodbank and get him to give you a couple of bags of blood, and then inject as much as you can into your veins, If you push down on the plunger and it won't go in anymore, you know you're good. Then go to the doctor. He'll try to take your blood pressure and it just won't work! Classic!

Another good one. When they ask you to piss in a cup, and they let you go back, shit in it! Then go back and hand back the cup all cool like. Haha! Try to keep a straight face!

Now come up with some of your own!