One key role, that of the Sarkhanese Prime Minister, was filled quite capably by a non-professional, Kukrit Pramoj, a prominent Thai newspaper publisher, former Thai Finance Minister, and, as fate would have it, future Prime Minister (1975-76). Speaking in Bangkok the day after its world premiere, the film's star, Marlon Brando, brought forth gasps by labeling his precocious co-star a "dissembler, liar and thief." Before shock could turn to indignation, Brando, straight face intact, quickly broke the stunned silence. "Mr. Kukrit told me he couldn't act, and then proceeded to prove he could act and, in fact, acted me off the screen. He stole the whole show."
Having previously met then Senator John F. Kennedy, and been particularly "impressed [by] the distinguished cut of his suit," director George Englund had all of Marlon Brando's suits made by the President's personal tailor, Sam Harris.
Two months after the film's release, a syndicated story appeared, entitled "Why Can't the Movie Be More Like the Book," written by one of the source novel's two co-authors, Eugene Burdick. Notwithstanding the article's title and the general critical consensus regarding the film's lack of fidelity to his book, Burdick's own assessment was surprisingly positive. While acknowledging that the film bears "only the most passing resemblance" to his novel, he views this as a plus, seeing 'the picture [a]s better than the book; more integrated, more skillful, and more dramatic," noting that director George Englund and screenwriter Stewart Stern had "crept inside the characters" that he himself "knew only as deeply as ink prints on paper." Moreover, Burdick commends Englund and Stern for "work[ing] much harder than had Lederer and [he]" to flesh out the fictional nation of Sarkhan, while marveling at actor Marlon Brando's ability to inconspicuously "slide into one's mind," then seamlessly integrate the information obtained thereby. Finally, despite noting the myriad changes made to his tale in its journey from printed page to projected image, Burdick can mount only the faintest show of reluctance before conceding that his novel's "political impact is still there."
When Marlon Brando takes a sip of champagne, smiles, and says, "Man, that's coffee," he is alluding to a joke told in the hit play Mary, Mary, by Jean Kerr, which ran on Broadway 1961-64. Mary says she has seen an obviously tired announcer on live TV late at night doing a commercial who took a puff of a cigarette, exhaled, and said, with a big smile, "Man, that's real coffee." The anecdote became well known even to people who had not seen the play and the line was, at the time, used to jokingly praise something that was obviously not coffee.
Director George Englund later stated in the TCM documentary about Marlon Brando that even though they were friends, later on in the filming process Brando started to "rebel" against Englund's instructions / suggestions and became very difficult to direct. There was one specific scene which Englund felt deserved a more emotional response from Brando. Brando passively refused to do it for multiple takes, until, exasperated, Englund called for an hour break. In the TCM documentary, Englund said "Sooner or later he had to do it to you. He had to castrate the father figure" --- in this case, the director.