Kate Mara has been trying to wean herself from plastic water bottles. "I'm trying to do the whole thermos thing. That's something I'm getting much better at," says Mara ("127 Hours," "Happythankyoumoreplease"), who also brings her own bags to the grocery store. "It isn't a lot but it's better than nothing," she says.

Mara plays aspiring singer Mississippi in "Happythankyoumoreplease," and was nervous about her big cabaret number. In the past, "I did a lot of musical theater and Broadway was always my dream, but as soon as I got the part I was equally horrified and excited to be able to sing at the end. I had a lot of trust in Josh [Radnor] as the director so I wasn't worried," says Mara, although because of the intimate setting she still found it "so much more horrifying" than singing the National Anthem in a stadium, which she's done before.

Originally from Westchester, she loved shooting the movie in New York ("On the weekends I went home") and working with Radnor. "He was very specific about what he wanted, which I love and crave in a director. At the same time, if I wanted to try anything, he was so open and supportive of it. I'd love to work with him again as a director and I would also love to act with him again for sure."

She'd also love to sing in an animated Disney flick, "be in more than ten minutes of a Danny Boyle movie," and work with younger sister Rooney ("The Social Network"). "It'll happen for sure one day. One hundred percent," vows Mara, who's been acting professionally since she was 14. She has several films awaiting release including "Ten Year," about a high school reunion, the medieval era-set "Ironclad" with Paul Giamatti, and "Peep World," a dark comedy with Michael C. Hall and Sarah Silverman, due out March 25. "That was a really fun shoot," she recalls. "I laughed the whole way through that one."

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