"Doctor Who" keeps it green on the set by reducing paper and plastic waste. "It sounds small, but we try to cut down on things like plastic cups and things like that. We try to use mugs," says star Matt Smith, noting that the cast gets scripts electronically to cut down on paper. At home, "I recycle everything," he notes, and so does co-star Karen Gillan, who shops at vintage stores. "I always buy secondhand clothes," she says.

The pair returns in new episodes of the time travel series on BBC America starting Aug. 27. "It's going to take some twists and turns. All relationships and the whole dynamic are going to change after the big revelation at the end of the last half of the series," says Gillan. "There's the great revelation, probably the biggest of the series," promises Smith, pronouncing the opener, "Let's Kill Hitler," "may be my favorite episode to date. It just rockets along, and the payoff to all these revelations is exactly what you would want it to be. It doesn't disappoint."

The latest in a long line of actors to play Doctor Who, Smith raves both about the part and the experience. "What's wonderful about him is he doesn't dismiss anything. He's not cynical. He's open to every single facet of the universe. I think that's a remarkable place to be in." The resultant fame "very much places you in the public eye in a more dramatic sense," he acknowledges. "There's always a bit of career pressure that comes with playing a role like the Doctor and being involved with this show, but I think it translated as a good pressure. It's about delivering and doing it justice, making it as brilliant as it should be."

Gillan, who plays the Doctor's companion, Amy, has been pleasantly surprised by audience response. "We film for nine months of the year and when we're shooting we're in this little bubble. You almost forget that it transmits to a lot of places in the world. We go to something like Comic-Con and realize how many people actually watch the show. We were in San Diego, running into people dressed up as us. It was the most bizarre, surreal thing," she says. "I hadn’t really done much before 'Doctor Who' so it’s pretty much transformed my career."

She recently shot "We'll Take Manhattan," playing '60s supermodel Jean Shrimpton in a story about her love affair with photographer David Bailey. "She was completely iconic, but weirdly not really remembered compared to someone like Twiggy who actually came after her. But I knew about her because I'm sort of interested in photography," notes Gillan, who has familiarity with the modeling world, having been scouted while tending bar in London while going on auditions. "I thought it had to be a better way of subsidizing myself," she reasoned. "I did some runway stuff and some sort of campaigns and editorials. I know what it's like to go to eight castings a day and traipse around. So I didn't have to learn about what a model's life was like." She also "was in my absolute element" in the mod '60s wardrobe in the movie, which airs on the U.K.'s BBC4 in October and is slated to air in Ovation in the U.S.

As for dream roles, both co-stars are on the same page — or maybe, stage. "I want to be Lady Macbeth," says Gillan. "And I want to be Macbeth," says Smith. "Let's do that!"

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