You pull up to the left of another cyclist stopped at a light, with your bike in neutral and your sidestand down, about arms length away. He can't see your sidestand because you are on his left. He assumes that since you are holding the clutch, that your bike is in gear. Reach over and push him on his left shoulder with your right hand, but not real hard. He will instinctually put his right foot down if it isn't already. Push him again, a little harder, and try to get him to push you back. When he does, fake losing your balance and fall off your bike on the left side. As he sees you fall and your bike tip, he will freak, thinking that he has caused your bike to go over, until he realizes that it's not going all the way because of the sidestand. The only risk is that he may actually drop his bike trying to catch yours. Done correctly, it is really funny. This was totally unexpected, and it was the first time I have ever seen it done in public.