Magician notices a rope hanging from his sleeve which pulls out about 12 feet until it's stuck. He finds the other end of the rope in his pant leg. He pulls that end, only to find the opposite end of his other pant leg, so he repeats pulling the ropes end. The audience will scream. Complete with rope, shorts, and instructions.
Two short pieces of rope magically turn into one long piece. Then the rope grows two extra ends, becoming a rope with 4 ends. Finally a knot tied on the rope multiplies to 3 knots. Full apparatus and illustrated instructions enclosed.