Jon Hamm has joined the cast of the 'Mean Girls' musical movie.

The 52-year-old actor will take on the role of Coach Carr, the gym coach and incompetent sex-ed teacher, in the upcoming movie adaptation of the Broadway musical, according to The Hollywood Reporter.

Meanwhile, Busy Philipps recently joined the cast as Mrs. George, the mother of Regina George, who will be played by Renée Rapp in the film.

Philipps shared a Deadline article revealing her casting, and wrote on Instagram: "You know something? I really never have been a regular mom… #meangirls (sic)"

Angourie Rice, Auli’i Cravalho, and Jaquel Spivey are also set to star in the movie, which will be directed by Samantha Jayne and Arturo Perez Jr.

Tina Fey and her husband Jeff Richmond are adapting their musical for the big screen, and they want the 'Mean Girls' musical movie to have a "fresher palette".

Composer Richmond told THR previously: "Right now, the day-to-day is more about the movie adaptation that we’re working on. We’re super involved with that. What we’re trying to do [with the movie] is take the score that sounds like a Broadway score - in a good way - and [give] the movie a fresher palette. To make it sound more like stuff you want to listen to on Spotify, as opposed to when you’re sitting eighth row at a Broadway show or the Pantages. It’s kind of making it a fresher, younger take on the whole thing. We’re kind of reinvented the music for the movie, so it’s really fun."

Lorne Michaels is producing the movie for Paramount Pictures, with Fey penning the script and Richmond and lyricist Nell Benjamin working on the music.

Richmond admitted he and Fey love working together.

He said: "We know when to get out of each other’s way when we’re working together. Like who’s taking this part? Who’s doing that? Who needs to push harder on getting the script done for this? We’re just around each other all the time. Same office, all the time. She’s a hilariously fun person to be around.”