"I'd first auditioned for Regina, and I'd flown out to L.A. for the first time with my mother. It was very exciting," Seyfried, who was 17 at the time, said of her first film role. "I met (Gretchen Wieners actress) Lacey Chabert for the first time, and Lindsay Lohan was in the room and Blake Lively was playing Karen, and then I was Regina."
"I flew home, and they were like, 'You know what, let's - we think you're more correct for Karen,' so I was like, 'Oh, God, okay, sure,' " she added of the casting process. 'Mean Girls' casting director Marci Liroff once told Cosmopolitan UK that while the production initially wanted Lively, who had not yet rose to fame for 2005's Sisterhood of the Traveling Pants, to play Karen, producer Lorne Michaels ultimately suggested casting Seyfried in the role.
"(Lively) came down to the final tests but, at some point, some of the filmmakers said to keep looking," Liroff said during a 2019 interview with the outlet.
"Amanda Seyfried had read for Regina and we really liked her but then Lorne suggested, 'Why don't we make her Karen?'"