The simplest practical joke I ever heard was in "The Complete Practical Joker" (which I can not find on Amazon.com).
Hugh Troy presumably went to NYC with a long rope. Near one intersection, he handed one end of the rope to an innocent victim and asked him to hold it for him for a minute. He then went around the corner and did the same thing with a second victim. He then disappeared down a subway entrance. So none of us know what happened, but it is pleasing to speculate.