If you think Will Smith is cheerful now, you should have seen him 20 years ago!
"Now, I'm bouncy. Back then, I'm sure I was quite irritating," Smith tells ET with a laugh.
WATCH: Will Smith Reveals the Film He Regrets Making: 'I Wanted to Be the Biggest Movie Star'
Two decades ago, Smith was entering a new chapter in his life and career when his popular '90s sitcom, The Fresh Prince of Bel-Air, came to end. While promoting his new movie, Collateral Beauty, the 48-year-old Oscar-nominated actor acknowledged that he's heard rumblings about a possible reboot of the show, but he doesn't plan to participate.
"I'm not doing it," Smith says simply. "If somebody wanted to, I would probably let them, but I have no intention."
Smith pointed out that the '90s seemed to be the perfect time period for the show and isn't sure how a reboot would play today. While it's true that many things have changed in the 20 years since Fresh Prince wrapped up, Smith's youthful appearance has remained the same, and he speculated on the key to his ageless look.
EXCLUSIVE: Muhammad Ali's Daughter Laila Says Will Smith's Portrayal of Her Father Was 'Phenomenal'
"There's a natural silliness that I gravitate to, so I think more than looking the same, I think energetically there's a fun and a zeal and a joy that I embody that gives that impression," he says. "I really enjoy what I do. I have fun every day in my life."
The veteran movie star plays a more somber role in Collateral Beauty. In the movie, a successful New York advertising executive (Smith) suffers a tragedy, which causes him to withdraw from his life. While his concerned friends try desperately to reconnect with him, he seeks answers from the universe by writing letters to Love, Time and Death, all of which visit him in different forms.
Dame Helen Mirren, 71, also stars in the movie, which she considered a learning experience.
"I have to say, I was in the learning seat on set with Will, because he is the star that he is, obviously, and he was leading our little cavalry," Mirren shares. "We're all sort of galloping along behind him."
READ: 'Independence Day' Director Roland Emmerich Says Will Smith Not Signing Up for Sequel 'Was Disappointing'
Mirren herself has also aged well and she's showing the world how youthful she still looks in new unaltered photos for Pirelli's 2017 calendar.
"All credit to them to step up to the plate and actually do it," Mirren says. "This is another idea of beauty."
Collateral Beauty hits theaters Dec. 16.