Today is Olsenboye day.

It's the day Mary-Kate and Ashley Olsen's full-fledged junior collection hits 600 JCPenney stores nationwide and the retailer's Website.

To celebrate the launch, JCPenney and the Olsens hosted a party at New York City's Norwood, a private club in Greenwich Village that was packed with well-wishers.

"I think it's going to be great," shoe guru Steve Madden told StyleList. His company is collaborating with the ladies on Olsenboye shoes as well as the design duo's more expensive Elizabeth & James footwear.

"I think the combination of the two of us, I mean the three of us, it's going to be great," he said.

While the Olsens were not speaking to the press, and instead chatting with select friends, they did address one blaring issue. "The twins want to talk -- turn the music down," a public relations girl was heard screaming into her headset. Moments later, the music was at a noticeably lower level.

JCPenney's President of Women's Apparel, Liz Sweeney, shared the next big Olsenboye treat -- the "spectacular" TV commercial that will air during the 2010 Academy Awards telecast on March 7.

In addition, the Olsens will be showing their high end line, The Row, at New York Fashion Week.