Along with a couple hundred of her good friends and family members, I helped celebrate the forty-fifth birthday of Robin Arnold this evening, at a once-in-a-lifetime party held at the Old Oaks Country Club, in Purchase, New York. I first met Robin and her husband, Steven, and their kids, Zack and Remy, on a cruise to Antarctica, in 2003. We've stayed in touch ever since. They're an amazing family, full of life and always up for a party. Robin, who looks about 25 and has the energy to match, rang in the occasion with special guest star Ja Rule, who showed up to perform several songs as the birthday girl (who's a huge fan) danced right along. Impressively enough, she also seemed to know every lyric. The Arnolds' friends are party people, no question. The dance floor was packed all night long and guests didn't start making their way home till well after midnight. What everyone surely wondered as they headed out was: How can the Arnolds possibly top this one?For more pix from the party, click here.