Lily Collins got "goosebumps" when she tried on Audrey Hepburn's sunglasses for one of her Emily in Paris looks.
The star's character Emily Cooper goes skiing in one episode of the new season and costume designer Marylin Fitoussi wanted to capitalise on Collins's resemblance to the Breakfast at Tiffany's legend.
Fitoussi suggested recreating Hepburn's ski look from the 1963 film Charade, complete with black faux fur garments and a pair of oversized Pierre Marly sunglasses - and they managed to obtain a copy of the original eyewear.
"When Lily tried them on, we were crying, shouting and having goosebumps. Every season we have a tribute to Audrey Hepburn, it's part of the game now," Fitoussi told WWD, adding that Pierre Marly reproduced the sunglasses for the series.
The original sunglasses are on display at the Musée de la Lunette in Morez, France.
That isn't the only homage to Hepburn in the fourth season. For the masquerade ball scene, Fitoussi wanted to reference Truman Capote's Black and White Ball in 1966 and tapped Nina Ricci creative director Harris Reed to design three outfits.
Reed, Fitoussi and Collins opted for a black and white jumpsuit with an attachable skirt that took inspiration from Hepburn's look in My Fair Lady.
Collins's wardrobe this season also features clothes by the likes of Jacquemus, Marni, Miu Miu and Boss, among others.
The first part of season four debuted on Netflix on Thursday. The second part will be released on 12 September.