The role of Stanley in Elia Kazan's 1951 cinematic adaptation of Tennessee Williams' 1947A Streetcar Named Desire represents the polar-opposite of Blanche (Vivien Leigh), and it is a role that requires a physically strong individual to pull of the temper, yet a street-savvy and rough-edged dialect, and Marlon Brando represented all that the character should be.
Despite that many people remember Brando as being a overweight actor as he aged, as a young man he represented the exact opposite. He was fit, powerful on screen and stage, and had a speech pattern that will be imitated throughout the years, whether for Streetcar, Waterfront, or The Godfather. It is his style of acting that made it possible for him to accurately portray the role of Stanley.
The most notable aspect of his portrayal is his voice and speech patterns. In nearly every film Brando had his own personal style. In Streetcar his at times garbled and quick delivery represents the area in which the character lived. He might not have grown up in the same environment as Blanche and Stella, but he was still a quick-witted man that knew the signs of a hustle. He had no need to use proper pronunciation; those living where he did did not speak like that.
Brando's physical appearance complemented the character he was playing and matched the stereotype for the way he spoke. Brando could be extremely intense, allowing the scenes where he looses his temper to become effective. Even as he, in his drunken state, calls for Stella (Kim Hunter), one can sense the passion of the character coming through the actor.
The audience can also pick up on the confidence within Stanley. There are times in Streetcar where a smirk comes across Brando's face as though he is proud of himself for revealing Blanches' past. A common actor would not be able to show the multiple layers within Stanley and might have played him only as a common brute, instead of a man with distinct intentions and plans.
Brando was the perfect actor at the time for the role of Stanley. He created a memorable character that will last throughout the future of the film industry.