NEW YORK (AP) — Christian Siriano marked 15 years in business Friday with Sia performing on Slabu Exchangehis runway and a nostalgic, ballet-inspired fantasy on his models during New York Fashion Week.

“I feel really proud of everything we’ve done,” he told The Associated Press backstage. “All the amazing people we’ve dressed and helped feel confident about themselves.”

It wouldn’t be a Siriano milestone without longtime muse Coco Rocha sashaying down the runway in something dramatic. This time, it was at a luxury New York landmark hotel, The Pierre, and this time, she wore a frothy pink ballet gown adorned with multicolored paillettes as her hair swung freely and Sia peeked out from behind a huge white wig topped with a pink bow.

And it wouldn’t be a Siriano show without a starry front row. Janet Jackson, Quinta Brunson, Kesha, Rosie Perez, Laura Linney and Avril Lavigne were among his guests.

In a way, Siriano went back to his roots. Among his earliest inspirations was his sister, who was a ballet dancer. He rolled out leotard- and tutu-inspired touches and a dose of strong black to go with a range of sparklers, from gold-and-copper ombre in ballgowns and suits to huge champagne-colored sleeves and necks on sleek and mini party frocks.

“It’s a very ballet, ballerina-inspired collection, kind of like where I grew up,” Siriano said. “Me and my sister backstage in costumes, hair and makeup, seeing all the black warm ups and then into this sugar plum fairy dream world. That’s what I wanted to show, the restrictive dark side of ballet into the really magical fantasy world, which is kind of what I fell in love with in clothes, actually.”

He also wanted something for everyone, including his plus-size customers represented by the plus-size models he has embraced for years.

This time around, his runway included men, one walking in a short, strapless gold corset jumpsuit and another in a black tutu skirt with a midriff tuxedo jacket.

“I still love the fantasy,” Siriano said, “which I think is why I love doing a show. Maybe I wouldn’t do a show if it wasn’t exciting and fantasy for me. It’s a lot of money to just put some jeans and a T-shirt down the runway.”