Jon Hamm as Don Draper/Dick Whitman
Where you probably saw him before the show: In supporting roles in the films of his ex-partner, Jennifer Westfeldt: Kissing Jessica Stein and Ira and Abby. Also in supporting roles on '00s TV series Providence, The Division, and What About Brian.
Where you’ve probably seen him after the show: As the Reverend Richard Wayne Gary Wayne on Unbreakable Kimmy Schmidt and as Falcon on Wet Hot American Summer: First Day of Camp.
John Slattery as Roger Sterling
Where you probably remember him from before the show: As Carrie's politician boyfriend, Bill Kelley, who was into watersports on Sex and the City.
Where you’ve probably seen him after the show: As Howard Stark in Captain America: Civil War and Ant-Man. He also appeared on the TV series Veep as Charlie Baird.
Christina Hendricks as Joan Holloway
Where you probably remember her from before the show: As the con artist Saffron on Firefly.
Where you’ve probably seen her after the show: As Celine on Comedy Central's Another Period and, most recently, the film Fist Fight.
January Jones as Betty Draper
Where you probably saw her before the show: In small supporting roles in the movies Anger Management, American Wedding, and We Are Marshall.
Where you’ve probably seen her after the show: As Melissa Chartres on Fox's The Last Man on Earth.
Aaron Staton as Ken Cosgrove
Where you probably saw him before the show: As Daniel on three episodes of 7th Heaven.
Where you’ve probably seen him after the show: As Mr. Donellen on Showtime's Ray Donovan and as JD on Girlfriends' Guide to Divorce.
Rich Sommer as Harry Crane
Where you probably remember him from before the show: As Andy's friend Doug in The Devil Wears Prada.
Where you’ve probably seen him after the show: As Robert in the 2016 film Hello, My Name Is Doris and as Dustin on Netflix's Love.
Vincent Kartheiser as Pete Campbell
Where you probably remember him from before the show: As Connor on Angel.
Where you’ve probably seen him after the show: As Jordan Anderson on Hulu's Casual.
Elisabeth Moss as Peggy Olson
Where you probably remember her from before the show: As the president's daughter, Zoey Bartlet, on The West Wing.
Where you’ve probably seen her after the show: As Offred/June Osborne on Hulu's The Handmaid's Tale.
CORRECTION
Jon Hamm's character's name was misspelled in a previous version of this post — clearly I had too many martinis at lunch.