the major change southern and kubrick made was to recast the script as a black comedy, jettisoning the "film within a film" structure. kubrick, george, and southern shared the screenplay credits, but competing claims about who contributed what led to confusion and some conflict among the three men after the film's release. the credit question was further confused by sellers' numerous ad libbed contributions—he would often improvise wildly on set, so kubrick made sure that sellers had as much camera 'coverage' as possible during his scenes, in order to capture these spontaneous inspirations.