Amanda Seyfried’s ‘Mean Girls’-Inspired Halloween Costume Is So Fetch: ‘I’m a Mouse’

Amanda Seyfried gave Mean Girls fans a laugh with her latest Halloween costume.

"I'm a mouse," the actress, 37, captioned a selfie that showed her wearing gray mouse ears. Seyfried — who shares daughter Nina, 6, and son Thomas, 3, with husband Thomas Sadoski — posed next to someone dressed in a bear mask.

The caption and costume, of course, reference the 2004 comedy. Mean Girls features a Halloween sequence in which new student Cady Heron (Lindsay Lohan) learns that scary costumes aren't what teenage girls typically wear on Halloween.

"In the regular world, Halloween is when children dress up in costumes and beg for candy," she explains in the film. "In girl world, Halloween is the one night a year where a girl can dress like a total slut and no other girls can say anything about it. The hardcore girls just wear lingerie and some form of animal ears."

Amanda Seyfried’s Rare Photos With Her Kids, Parenting Quotes Over the Years

Gretchen Wieners (Lacey Chabert), clad in a leather dress and cat ears, arrives at Karen Smith's (Seyfried) house before the Halloween party. Karen opens up the door in a sexy black nightie with mouse ears. "What are you supposed to be?" Karen asks.

"I'm a mouse. Duh," Karen says.

Unlike Karen, Seyfried opted to pair her mouse ears with a cozy navy sweater.

While Seyfried now has a stacked resume with leading roles in Mamma Mia!, Les Misérables and The Dropout, Mean Girls was her first movie. She'd only been on soap operas All My Children and As the World Turns prior.

"I think the reason I got Karen was because I played that person in high school in order to stay out of drama," Seyfried told Vanity Fair in February. "It was a much easier transition into playing Karen from where I was at in my life at that point. I was only 17, so high school was like right there."

‘Mean Girls’ Cast: Where Are They Now?

She understands why audiences are still attached to Karen nearly 20 years later. "I think the reason we love Karen so much and also the reason that she's so funny is that she is just being brutally honest," Seyfried said. "It's so beautiful and it's what makes her so endearing, and she's not that smart but she totally knows it. And everything that she reacts to is just her truth, her true reaction. I think we all love people like that because we can trust them."

Karen will be back on the big screen when MEAN GIRLS hits theaters in January. It isn't known if Seyfried will make a cameo in the adaptation of the Broadway musical, but she teased that she was hopeful earlier this year. “It’s been a long legacy for Mean Girls and I think we all kinda need to hang,” she told Entertainment Tonight in February of her former castmates, noting she’s “still hoping for a miracle” when it comes to returning for a cameo.