jessica simpson

Jessica Simpson serves as guest judge at the "Project Runway" Spring 2011 fashion show. Photo: Bryan Bedder, Getty Images for IMG

Jessica Simpson strode onto the catwalk of the biggest venue of Mercedes-Benz Fashion Week as the surprise guest judge of the "Project Runway" show on Sept. 9, flanked by host Heidi Klum and hosts Michael Kors and Nina Garcia.

"I love fashion, and I'm a big fan of the show," Simpson, wearing a sparkling black dress ("I'm from Texas -- I love sequins!") and Bavna earrings, was heard gushing. "I thought the designers did a really good job."

Tim Gunn told StyleList he had been backstage with the designers since 4:45 a.m and earned a few more white hairs:

"They were all having this out-of-body experience. It gave them chills, it inspires tears. And the last-minute changes! In a couple of cases, I stepped in. I said, 'I don't know where this pant came from, it's dreadful, and I did not see yesterday.' It's not like me, but I was losing my patience!"

Meanwhile, Klum told us, "I'm so excited to see this show, I haven't seen [what they're presenting] yet. We say on 'Project Runway,' 'One day you're in, and the next you're out,' and it's so true."

This season, the contestants were "very emotional, very soft," she said, indicating that some of the competitors got especially upset after they were eliminated. "Just because we say in one challenge, 'You're out,' doesn't mean you should never design again. It doesn't mean you are bad or your design is awful; it just means you are the weakest one. It's challenge by challenge."

heidi klum tim gunn

Tim Gunn and Heidi Klum at the "Project Runway" show. Photo: Andrew H. Walker | Bryan Bedder, Getty Images for IMG

Klum, wearing a flame-red pantsuit with a cowl-necked blouse and fitted jacket, said "definitely suits" were her pick for trend of the season. She's also wearing been a lot of Phillip Lim lately, including one of his men's suits for her recent City magazine cover shoot.

"It's menswear for women," she said, adding, "Probably the opposite of what I like to wear! I like feminine, I like to dress like a woman."

Jamie-Lynn Sigler, Jordin Sparks, Tyson Beckford and "Project Runway" producer Harvey Weinstein were just a few of the famous faces in the front row.

Sigler told us her favorite trends of the season are "all the jewel-tones, I think they're beautiful." Weinstein said Lifetime persuaded him to extend the show to 90 minutes per episode for the eighth season, even though he was initially hesitant. "But it really worked," he says. "I think I'd do a four-hour episode of 'Project Runway' now!'"

Prior to the show, StyleList caught up with Joanna Coles, editor of "Project Runway" magazine partner Marie Claire, as well as Hearst magazine chairman Cathie Black.

"We're obsessed with 'Project Runway!'" said Coles. "We have Tim Gunn in the magazine every month and many of the 'Project Runway' designers have been successful and gone on to have their own lines. It's surprising how many have gone on to be really viable businesspeople."

Asked if the ladies had a favorite contestant from the current season, Black demurred that she had to "stay neutral."

"Cathy is a lot more diplomatic, but I don't have to be," Coles said with a smile. "Obviously Gretchen!"

For more on Fashion Week Spring 2011, click here.