"Our love fern never died," Hahn laughed of the 2003 rom-com, in which she played BFF to Hudson's character, Andie Anderson, a journalist who falls in love with Matthew McConaughey when she tries to fake a relationship with him to write her next big feature.
"It was such an impressionable time for us," Hudson recalled of making the film. "We were just, you know, really starting out and babies and we really did- I felt when I met Kathryn the first time, it felt familial. It was like family, and we had so much fun."
"It was my first movie," Hahn agreed, saying of meeting Hudson for the first time, "I'll never forget being like, first of all, that's a movie star. And second of all, I was like, she's so normal and so cool and just the best."
"I just always was like, Kate Hudson is a miracle," she added. "And then just to see it come full circle and see her freakin' kill it -- pardon my French -- in this movie... it's just so thrilling."
How to Lose a Guy has some iconic fashion moments, however, Hudson's Glass Onion character -- a supermodel-turned-designer named Birdie Jay -- might take the cake with her epic ensembles. Hudson and Hahn had a laugh with ET about how different their wardrobe fittings were, as Hahn plays a much more buttoned-up character: Claire Debella, the governor of Connecticut and a candidate for Senate.
"I walked in and it was like someone had thrown just, like, colors and prints and sparkles and hats all over the fitting room, and then Kathryn had, like, a rack of beige items," Hudson recalled.
"I was just like, beige, and then flats," Hahn agreed with a laugh. "It was very funny."
A Hollywood insider since birth, Hudson has likely known plenty of "Birdie Jay" types throughout her life. However, she said she didn't base the character on anyone in particular.
"I'm sure a lot of people will kind of see someone they know or an idea of something in Birdie, Hudson said. "I just wanted to bring what I could bring to what Rian put on the page and not kind of complicate it with trying to be thinking about someone else."
As for the rapid-fire murder mystery questions about their castmates, while the duo said they would trust most of their Glass Onion co-stars to help them hide a body, they definitely had more specifics about who they would let tweet for them for an entire week.
"Leslie [Odom Jr.], class act," Hudson answered. "Daniel [Craig], absolutely not. Daniel would be a disaster. You'd be like, 'Oh my god, you've ruined my entire career!'"
"He would have so much fun," Hahn agreed.
Glass Onion: A Knives Out Mystery will have a limited theatrical release starting Nov. 23 before streaming on Netflix on Dec. 23.