When it comes to pick-up lines, Mary-Kate Olsen gives points for originality.

Asked by Conan O'Brien on his Late Night show Wednesday if guys ever approached her on the streets of New York to "take a shot" at asking her out, Olsen replied, "Occasionally they do come up, but they say the weirdest things sometimes."

One of the weirdest: "The other day somebody asked me if he could make me tomato soup," she said, laughing.

A shocked – and impressed – O'Brien quipped: "What? A guy tried that? I respect that guy so much, I really do."

Apparently so does Olsen, who deadpanned, "I looked at him and said, 'I love tomato soup.' And now I'm pregnant."

In terms of her real taste in guys, she revealed that she fancies O'Brien himself. "I just have to say, I am a huge fan. I have a bit of a crush," she said at the beginning of the show, and complimented his hair.

Olsen, who was on show to promote her new role as a Christian pot smoker on Weeds, also said she has a sense of humor about living in the spotlight with her twin sister, Ashley. "Sometimes if I'm out I'll say I'm Ashley or if I'm making reservations for a restaurant I'll use my sister's name – actually most of the time," she told O'Brien.

She also confessed to an obsession with coffee and says the reason she is often photographed carrying a Starbucks cup, is that going to the coffee chain, "Is the only time I leave my house or get out of my car to go somewhere."

She added: "Ever since I was young I have loved the taste of coffee." She didn't say how young – but it started when she used to sneak a cup of coffee up to "the playroom."