Johnston made her professional stage debut with New York's Atlantic Theater Company, which was founded by playwright David Mamet. During her association with that company, she appeared in such productions as As You Like It and Stage Door, among many others. She has performed with the Naked Angels Theater Company in The Stand-In and Hot Keys, and with New York Stage and Film in Kim's Sister, with David Strathairn and Jane Adams. For her performance in The Lights at Lincoln Center Theater, Johnston was nominated for a Drama Desk Award as Best Supporting Actress. The show brought her to the attention of a Carsey-Werner television executive. After numerous auditions in 1996 for the TV series 3rd Rock from the Sun, she won the role of Sally Solomon. She starred in the series from 1996 to 2001. The role earned her two Emmy Awards for Outstanding Supporting Actress in a Comedy Series. She made her feature film debut in The Debt, winner of Best Short at the 1993 Cannes Film Festival. In 1995, she played Kate in the film Backfire! She played Esmeralda, a sea hag in Thrill Ride, a family friendly film released in 2016. Other television credits include guest-starring roles on the series Chicago Hope, Hearts Afire, and The 5 Mrs. Buchanans. She was also the narrator in Microscopic Milton on the Disney Channel. Her significant roles in commercially successful movies included in 1999, Ice Age, and Music and Lyrics in 2007. In 1998, she was a spokesmodel for the Clairol company, as well as appearing on Bad Religion's No Substance album cover. Johnston appeared in the sixth and final season of Sex and the City. In the episode entitled "", her character, Lexi Featherston, an aging party girl, accidentally falls out of a window and dies, prompting Carrie Bradshaw to re-examine her life. In 2005, Johnston was featured in six episodes of NBC's ER. She was cast as Patsy in a proposed American remake of the British TV showAbsolutely Fabulous, but the series was never picked up by a network. She appeared in a recurring role in the 2009 season of Ugly Betty and had a single-episode appearance as a dominatrix in the second season opener of Bored to Death. She starred in the TV Land sitcom The Exes, which ran for four seasons between November 30, 2011, and September 16, 2015. In 2018, she began a recurring role on the CBS sitcom Mom, and was upgraded to series regular for season 7.
Personal life
Her father was former Wisconsin Republican state senator Rod Johnston. In her autobiography, Guts: The Endless Follies and Tiny Triumphs of a Giant Disaster, Johnston discusses an addiction to alcohol and pills that began when she was in high school. She mentioned that at the height of her addiction she drank on average two bottles of wine per evening. She stated in the 2012 book that she had been sober for five years. Through her charity SLAM, NYC, she mentors high school girls from New York City with addiction and self-esteem issues and has been crusading for the city to build a recovery high school. Johnston said she was diagnosed in November 2013 with lupus myelitis, which caused her to miss filming for some episodes of her series The Exes. A character played by Leah Remini was introduced in season three to cover Johnston's absence.
Filmography
Film
Television
Stage
Autobiography
2012: Guts: The Endless Follies and Tiny Triumphs of a Giant Disaster., Gallery Books,
