Before principal photography began, Linson took a four-month crash course in directing. Thompson was eventually brought aboard the film's production as "executive consultant", but claimed he had no substantial role other than to have "wandered around and fired machine guns on the set". Kaye has claimed that Thompson and Murray changed parts of the script during filming and, at that point, he chose to no longer be involved in the production. Steadman observed Linson on the set and said that it was "pretty obvious that he was in no frame of mind to catch the abandoned pure essence of gonzo madness, which can only happen in uncontrolled conditions". He also felt that Linson's "fanaticism for the subject he was trying to portray was undoubtedly there, and his sincerity, too", but felt that he was under the impression that the film was a runaway hit before he had even begun filming it and therefore refused to take any chances with the material. Steadman and Thompson spent time on the set and the former talked to Murray about his impressions and observations of the latter's mannerisms. Within two weeks of Thompson being on set, Murray had transformed into him.