Heidi Montag hosted a pool party at the MGM Grand in Las Vegas on Saturday. She wore a sexy bikini for the event, where she posed for pictures with a giant beach ball and got playful with a bottle of champagne and a basket of fruit. Spencer Pratt was also on hand for the festivities, though he let Heidi have the spotlight. Heidi met up with fellow blonde Crystal Harris, who called off her marriage to Hugh Hefner earlier this week. Crystal celebrated in the sun on what would have been her wedding day while Hef screened the movie Runaway Bride at the Playboy Mansion with friends.