Playboy Magazine's Miss July/August 2009 Double Issue Playmates of the Month Karissa and Kristina Shannon signed autographs at the Playboy Store in Las Vegas on Friday. What do you think of Hugh Hefner's hotties? See more photos after the jump...

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19-year-old Karissa and Kristina will become the leading ladies in the upcoming season of The Girls Next Door since the first three girls have departed.

The twins replaced Bridget Marquardt and Kendra Wilkinson, while Crystal Harris replaced Holly Madison as Hefner's number-one girlfriend.

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Hef's exes have solidly moved on with their lives after moving out of the mansion. Kendra is expecting her first child, Bridget is busy visiting beaches for a Travel Channel show, and Holly has dated several men, including illusionist Criss Angel.

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