Ask the victim if they want to get high and see amazing colours. They usually say yes, and so the game shall begin. Place the victim (who, it must be said, has to be a very trusting victim) on their knees and hold a towel in front of their face. An accomplice would then pull the towel up while you pushed on either side of their nose with your palms. Once the towel is removed, ask them if they can see the flying colours. Obviously, they don't, so you try again. This time, however, press your arse against the victim's nose and teasingly drag the towel away. It might help if your accomplice presses their face forwards. It would seem a terrible waste to go through all this effort if their nose didn't go up your arse.