Since his first screen appearance in 1991, Jake Gyllenhaal has appeared in over 30 movies in lead and supporting roles. He has often opened up in featurettes about the sort of work he had to do during the film production, like - in the case of 'Nightcrawler' - how he has to lose a tremendous amount of weight and spend his time living a nocturnal existence in order to fully pass off his role as believable.