zombie84 said:

The second draft shortened it to just, "The Empire Strikes Back," which is saying the same thing. But then Lucas felt that the boxing idea was too real-world, so he changed it to a lightsaber match instead. Gary Kurtz suggested it would be better if he fought Luke instead of Darth Back, so that's where the climactic saber duel originated from. Darth Back was eventually cut down to a side character, and they even made prototype action figures of him, but his few scenes were all cut out. There have been bootleg prototype toys on eBay from time to time but none are authentic.

Sir Mix-a-Lot did the theme.