Emile de Ravin's character Claire Littleton hasn't been seen since the fourth season. She says viewers will be shocked with her return.
Actress Cynthia Watros, who played the character Libby before being killed off in the second season, will also return this year.
"The thing that I'm most excited about about season 6 is once again our characters in some bizarre way get to reinvent themselves," said Evangeline Lilly, who plays Kate Austen. "And that's happened, in my opinion, every season with different formulations and different combinations of people, and time, and space, and island, and all that. We once again get to reinvent our characters and I am very excited about that. It's a lot of fun, it keeps it spicy for us."
Josh Holloway's character James 'Sawyer' Ford has evolved unlike any other character of the show. He says fans can expect more action and even more changes in the final episodes.
"I have not expected any of these turns, so they've all been a surprise to me. And yes, he takes another turn," said Holloway. "But that's all I can tell you. I can say it's action packed baby!"
Jaws dropped at the end of season 5's finale, with fans questioning who John Locke really is and the new group arriving on the Island. Is Locke good? Is he bad? Will fans find out the truth behind the character?
"I have no want in how my character is wrapped up. I simply want it to be satisfying to the audience. I have no particular desire," said Terry O'Quinn, who plays Locke.
Mystery continues to surround the manipulating and devious former Other leader Benjamin Linus and his feud with Charles Widmore.
"I look for something dramatically satisfying, and it's fine with me if it is as ambiguous an ending as was his beginning," said Michael Emerson, who plays Ben.
The show's producers say when "Lost" ends in May, it's definitely over -- there won't be any spinoffs or sequels.
"Lost" kicks off with a 2-hour season premiere on Tuesday, Feb. 2 on ABC7.
