In the video, the entire cast struts and swirls up and down a fashion runway looking like seasoned pros, but Lea and Darren revealed that looks can be deceiving.
"[We were] trying to act cool like we knew what we were doing," Lea said with a giggle.
"I think you can see me laughing with delight," Darren added.
Fashion's Night Out is a late-night shopping extravaganza that took place in cities across the country on September 8 and Lea, who signed t-shirts for the first 150 fans, compared the experience to Mardi Gras.
"It's so fun," the actress gushed. "It's like the city becomes so alive."
Part of the proceeds from the FNO collection go to the New York City AIDS Fund in the New York Community Trust.
Click the video to hear how Lea and Darren plan to help their co-star Jane Lynch as she hosts the Primetime Emmys Sunday, September 18 on FOX.