Paris Hilton throws a party for Stavros Niarchos III

Hilton went all out for the fete and “spent at least $4,000 on party supplies,� says a source for Star magazine. Paris bought her supplies at LA party store, Party On. "She's been back and forth, buying plates, balloons and extravagant wrapping paper," the source said. "One time Paris flew in from Vegas and went straight to the store. Another time she left the store and went to the Beverly Center to buy more gifts for Stavros and came back for more wrapping paper."

The invitees for the occasion represented a veritable who’s who list of young Hollywood. Perez reports that Nicky Hilton, Kevin Connolly, Brett Ratner, Milla Jovovich, Vincent Gallo, Elisha Cuthbert, Kimberly Stewart, David Katzenberg, Brody Jenner, Andy Milonakis, Courtney Love and Lucas Haas all attended. The New York Daily News even claims that Hilton’s ex, Paris Latsis was on hand. The event was the first one that Paris has hosted in her home since renovating, says Perez. She playfully referred to her pad as Club Paris and later allowed her guests to swim in her pool fully clothed.

Paris must have gone to such great lengths because with the passing of Stavros’s birthday, the Greek shipping heir will reportedly now be worth $275 million. And not just that - Stavros can now legally join Paris for some legendary drinking binges. Another source told Star, "It's a relief for [Paris] to see [Stavros] finally turn 21 so he can make the bar rounds with him in peace. It's been a huge issue for them for months now, forcing them to stay home a lot more than Paris is used to."