Twentieth Century Fox

The Date Night poster with Tina Fey sporting a gorgeous (and totally destroyed) navy dress made the fashionistas among us flinch—and we couldn’t help tracking down the inside scoop. The film’s costumer designer Marlene Stewart (who also made Madonna’s wedding dress for her 1985 nuptials with Sean Penn!) created the silk charmeuse number with a few requirements in mind. We wanted it classic and sexy, but Tina had to be able to move for the action scenes,” she told us. “Plus, the director [Shawn Levy] didn’t want black, so we found a shade that looked good on film.” 10 identical versions of the dress were crafted, then sent to the  wardrobe department’s “ager/dyer,” who was tasked with making them look realistically damaged. The one part of the Stewart’s job that wasn’t so complicated? “Showing off Tina’s legs,” she said. “She has great legs!Date Night, which also stars Steve Carell, hits theaters April 9th.

See more photos: Mila Kunis, James Franco and Mark Wahlberg make sidesplitting appearances, while Leighton Meester plays a dutiful babysitter. What would Blair Waldorf think?