Sonnenfeld, who was with Smith throughout the series, jokingly added that fans would have to wait till 2030 for the sequel to the newest "Men In Black."
Although Smith's roles are more synonymous with action and comedy, he revealed the secret to his Academy Awards nominated performances in "The Pursuit of Happyness" and "Ali."
"I had great models," said Smith, explaining that he found he was a good mimic of people.
"In 'Pursuit of Happyness' I was using my father as a model."
Brolin, most famous for his role as former US President George W. Bush in "W" and "No Country for Old Men," expressed his adoration of highly acclaimed Korean director Park Chan-wook.
"His trilogy I find to be one of the best trilogies that I have ever seen," said Brolin, referring to Park's "Vengeance Trilogy."
Brolin will play the protagonist in Park's Cannes-winning "Oldboy" in the American remake of the film.
"I think director Park is one of the best directors not just in Korea but ever," said Brolin.
Smith is accompanied on his Seoul trip by his wife Jada and their daughter Willow Smith.
Prior to departing LAX, Will Smith laughingly brushed off divorce rumors that have recently surfaced in Hollywood.