On Episode V, go to the Cloud City level and defeat Darth Vader for the first time. After that, you will be playing as Leia, Lando, R2, and Chewy again. Find and rebuild C-3PO, then make sure your partner is C-3PO. Run around fighting off some troopers and, soon as you see C-3PO without arms and one leg, shoot him one more time. Note: This will not work if the troopers do it. He will return, but all you will see is his shadow on the ground. After a few seconds, he will be visible again. Repeat this as many times as desired.