2. Crossing The Streams Was Made Up On SetAfter tirelessly filming the rest of Ghostbusters, Harold Ramis and Dan Aykroyd were left with quite the conundrum how would they get the Ghostbusters out of the final stand-off with the Stay-Puft Marshmallow Man? These were simple mortals after all, going head-to-head with a Sumerian avatar of destruction. Did they really stand a chance? Despite plenty of rewrites, they were no closer to an answer and then it hit them. "The whole 'crossing the stream' thing, I think we invented," said Reitman. "I don't remember that in the screen play. When we were up there at the top of the building, struggling to come up with how we were going to get to the finish. I mean, how are we going to kill this guy once and for all?" Amused by the technobabble used to explain the heroes nuclear-powered proton packs, they decided that a potentially cataclysmic act was the best way forward and soon came up with crossing the streams. Its since become one of the most memorable scenes in cinema. And gave rise to the rather brilliant scientific explanations of what crossing the streams might do, by Dr. Egon Spengler. And to think it could have been so different.