'Project Runway' Preview: Heidi Klum Spills Secrets About Season 10

Heidi Klum and Co. are back on Lifetime starting Thursday when Project Runway returns for its 10th season.

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The show's stars -- host/judge/executive producer Klum, mentor Tim Gunn and judges Nina Garcia and Michael Kors -- took a break from their Runway duties while the network aired two spinoffs, Project Accessory and Project Runway All Stars, over the past year.

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For her part, Klum says that this season's crop of designers is a "mixed" bag of those who can and can't cut it on the show, as is typical of previous seasons, though she declined to compare the group to past contestants.

"It's always hard to compare because ... each year, fashion evolves and becomes different, and so do our designers," Klum said."I think we have some this season that are not that talented and you quickly see that, and some that are amazing and come up with new things and we go, 'Wow, we haven't seen anything like that.'"

The 16 designers include Gunnar Deatherage, a 22-year-old from Louisville, Ky., who viewers might recall was in the running for season nine but didn't make the final cut.

"He came last year and didn't make it; he made a dress that confused us," Klum said. "It was a swan-looking gown that was not very on trend or fashion-forward, a very Cinderella kind of old-school [garment]. But we really did believe in him, and I think he grew in the past year and showed us he had evolved as a designer."

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Klum also confirmed reports that two designers leave the show early this season, saying both "literally packed up their bags and ran off in the middle of the night." She said their actions left her shocked.

"This has never happened to us before," she said, adding that viewers will see the events play out. "You would think a grown-up would say, 'Thanks, I can't make it work, I gota go early.' But this is something a kid would do."

Meanwhile, Klum noted that this season will again employ a mix of traditional and unconventional challenges. The first will involve an outdoor runway show in New York's Times Square -- a Project Runway first -- that will involve two looks created by each designer.

Subsequent challenges will revolve around designing a costume for Radio City Music Hall's Rockettes, creating an outfit using candy and designing an item for one of Klum's lines.

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Klum added that actress Lauren Graham and stylist Patricia Field (The Devil Wears Prada, Sex and the City), who was a guest judge on the show's very first episode, will serve as guest judges for the Times Square challenge.

Other guest judges this season include actresses Hayden Panettiere and Krysten Ritter (Don't Trust the B in Apartment 23).

Project Runway's 10th season premieres at 9 p.m. Thursday.