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The boyfriend cardigan has never looked so sexy.

Gap's fall ads feature a gorgeous Liv Tyler wearing their boyfriend cardigan. And nothing else. But if anyone could convince us that wearing nothing but a couple of oversized cardigans looks good, it's got to be Liv.

Sexy celebrity advertising

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This year, Gap is going with a "Create Your Own Gap" campaign, encouraging people to mix and match pieces to create his or her own style, which of course they're hoping will mean you'll need lots of pieces to complete your look.

Liv isn't the only celeb involved in Gap's fall ad lineup. She'll be joined by stars like Ginnifer Goodwin, Hugh Dancy, and Sean Avery. We're betting Hugh and Sean wear pants.