Doc (Christopher Lloyd) and Darth Vader were fighting with light sabers -- Marty McFly (Michael Fox) and Luke Skywalker were in on the action, too. At some point Marty McFly killed Luke Skywalker. Then Doc killed Darth Vader. Somehow, then, Doc was fighting his evil twin, and then somehow the good Doc became evil, too. In the end, the one evil Doc killed off the other evil Doc, and the surviving evil Doc began walking towards me, swirling his light saber around in a circle. Then the end of the saber kind of 'broke' and the evil Doc cut off his own head. It sailed through the air and hit the ground, spewing blood. Doc's head croaked: "Entire life's work... up in smoke..." Marty McFly jumped up and shouted "DOC!" like in the movie. A group of tourists walked by, but they didn't notice anything.