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Those legs could stop traffic! Jessica Simpson struck a sultry, pinup-worthy pose in the backseat of a car on Saturday, June 21, and then took to Instagram to share the pic with her nearly 550,000 followers.

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The black-and-white shot shows the Weight Watchers spokeswoman, 33, reclining seductively in a car seat, her floral-print dress just barely skimming the tops of her thighs. Her lips are pursed into a perfect pout, and her long blond hair is tousled in big curls.

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It looks like an outtake from a sexy photo shoot -- but it's actually just a picture of Simpson slouching down to avoid being seen by photographers. "Hiding from the paparazzi, so why not pose for Eric?" she captioned the image, referring to fiance Eric Johnson.

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The mom of two -- she shares daughter Maxwell, 2, and son Ace, 12 months, with Johnson -- has been all about showing off her hot bod since she lost the weight she gained while pregnant. She regularly steps out in leg-baring, body-conscious frocks, and has also posted photos of herself working out.

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"I love this body and what it's capable of -- no matter what size," she said in a Weight Watchers ad earlier this year. "But this version feels really good."