Rachel McAdams said she “found out later” that fellow Plastics Lindsay Lohan, Amanda Seyfried and Lacey Chabert were participating in the ad

Rachel McAdams is explaining why she didn’t join a recent Mean Girls cast reunion that everyone agreed is so fetch.

In an interview with Variety published Wednesday, the Are You There God? It’s Me Margaret star commented on the Walmart commercial that brought back Lindsay Lohan, Amanda Seyfried, Lacey Chabert and more as their characters from 2004’s Tina Fey-penned movie Mean Girls.

“I guess I wasn’t that excited about doing a commercial if I’m being totally honest,” McAdams, 45, told the outlet. “I’ve never done commercials, and it just didn’t feel like my bag.”

She added that she “didn’t know that everyone” — including Lohan, Seyfried and Chabert as her fellow “Plastics” — was participating in the ad.

“I would, of course, always love to be part of a Mean Girls reunion and hang with my Plastics,” the actress continued. “But yeah, I found that out later.”

Lacey Chabert, Lindsay Lohan and Amanda Seyfried in a Walmart commercial spot.LUCIA ANIELLO/HUNGRY MAN

The commercial mixes showcasing holiday deals at Walmart with iconic Mean Girls scenes and began airing on Nov. 1. It offers glimpses of beloved North Shore High School characters as adults, including Cady Heron (Lohan) as a guidance counselor, Gretchen Wieners (Chabert) as a needy stage mom and Karen Smith (Seyfried) continuing her career as a clueless weather reporter. Kevin Gnapoor (Rajiv Surendra) and Damian (Daniel Franzese) also appear in the ad.

“It was so nice being back together after all these years,” Lohan told PEOPLE exclusively of being on another set with her former castmates. “It was great catching up with everyone.”

“It was wonderful to spend the day with Amanda and Lindsay,” said Chabert. “And it was so much fun getting to reminisce and be together again.”

McAdams — who played Queen Bee Regina George in the Mark Waters-directed hit film — told Variety that while a commercial wasn’t up her alley, “a movie sounded awesome.” Asked whether she made a cameo in the upcoming Mean Girls movie musical, McAdams said she and Fey did not film one.

“Tina and I sort of dabbled with a few ideas, but it was tough to make it all work in the end,” she said. “I was really down for whatever she wanted to do.”

Of the new screen adaptation of the Broadway musical, she added, “I think the direction it went in will be fantastic and I cannot wait to see it.”

(Left to right:) Lindsay Lohan, Amanda Seyfried, Lacey Chabert and Rachel McAdams in “Mean Girls”.

McAdams’ performance in this year’s Are You There God? It’s Me Margaret has earned nominations among critics groups, including a win from the Los Angeles Film Critics Association Awards. She told PEOPLE she accepted the role of what she’s called the “sexy mom” in the film adaptation of the classic Judy Blume novel because she was “a very fresh second-time mom” with her daughter.

“It was very, very in the forefront — what it is to raise a girl. I was so excited to have a girl. I didn’t even realize it until I found out I was having a girl,” said the actress, who also shares a 5-year-old son with longtime partner Jamie Linden.

“I remember thinking, ‘I would love this to be in the world for her one day,’ because it’s hard for parents and kids to talk about stuff,” McAdams said. “That’s never going to go away.”

Paramount Pictures will release the Broadway-to-screen Mean Girls musical, starring Renée Rapp, Angourie Rice, Busy Philipps, Jon Hamm, Auli’i Cravalho, Ashley Park and Fey, in theaters on Jan. 12.