Jason Reitman directed ‘Saturday Night’ as if it was a musical. The 46-year-old filmmaker is at the helm of the biographical comedy-drama that charts the story of how ‘Saturday Night Live’ made it to the television screen, and admitted that he approached the project as if it was a stage show rather than a movie. He told Collider: “You have to think of it like a musical. It’s like choreography. We have to organize where every character is at any given moment, and we shot the movie twice. We did the movie in prep, shooting it with stand-ins, camera, stills, video, figuring everything out. We bui…