The 39-year-old actress portrayed Regina George, the leader of The Plastics, in the 2004 movie, and doesn't seem to mind that she is still asked about the character.
"Does Regina George haunt me every day? She does have that quality," she quips in an interview with The New York Timesthat was published on Friday. "No, I have to thank Regina George for giving me some longevity. I’m forever grateful to Tina Fey [the Mean Girls screenwriter] and Mark Waters [the director]."
McAdams recalls going out for the coveted role, telling the newspaper, "I remember when I read it, I called my agent right away and said, 'I will play any part in this, please, please, please.' I was at the beginning of my career, and it was a lofty thing out there, that I really, really, really wanted to do."
She adds, "I’m always looking for larger-than-life characters, which is probably why I like playing villains. They get away with so much."
Tina Fey Jokes 'Mean Girls' Cast Is Too Expensive Now for a Sequel (Exclusive)
As for a Mean Girls sequel, Fey told ET that McAdams and her co-stars -- including Lindsay Lohan, Amanda Seyfried, Lacey Chabert and Amy Poehler -- have much higher salary requirements these days but encourages someone to "write it up."
"Their quotes are all too high now. They're all Oscar nominees," Fey -- who is behind the Mean Girls musical on Broadway -- said, referring to McAdams' Academy Award nomination in 2016 for Spotlight.
While there are no talks of a sequel just yet, McAdams has returned to comedy with her latest film, Game Night.
When it comes to her personal life, it was reported on Thursday that the actress is pregnant with her first child. ET reached out to her rep, who was not available for comment.