Marcia Wallace, an Emmy-winning character actress on two of TV's most enduring shows, has died. She was 70.

Wallace passed away Friday in Los Angeles. Her cause of death was not immediately announced, but Cathryn Michon, who co-wrote and directed Wallace's final movie, "Muffin Top," gave this statement to Deadline: "She passed at 9 p.m. last night due to complications from breast cancer of which she was a long and proud survivor and advocate for women and healing. Ironically it was during breast cancer awareness month during which she was always a funny ray of hope for so many. I’m devastated."

Wallace rose to fame in the 1970s as joke-cracking receptionist Carol Kester on "The Bob Newhart Show." The role of Kester was written specifically for Wallace after producers took note of her many appearances on "The Merv Griffin Show."

In 1992, Wallace earned an Emmy for her voice-over work on "The Simpsons" as Bart's long-suffering Springfield Elementary School teacher Edna Krabappel, who had an affinity for men, booze, and cigarettes. Wallace provided the pipes for other "Simpsons" characters, including Ms. Mellon in "Bart the Genius," Enchantra in "Marge Gamer," and Mrs. Krabapatra in "Simpsons Bible Stories."

In a statement to EW, "The Simpsons" producer Al Jean said, “I was tremendously saddened to learn this morning of the passing of the brilliant and gracious Marcia Wallace. She was beloved by all at 'The Simpsons,' and we intend to retire her irreplaceable character.” Jean added that Mrs. Krabappel would be retired on the animated comedy, now that Wallace has passed.

Wallace's quick wit and outsized personality made her a hilarious mainstay on the game-show circuit of the 1980s, appearing on "Hollywood Squares," "The $25,000 Pyramid," "Win, Lose or Draw," and "Match Game."

Wallace also starred in smaller roles on many popular TV series, such as "Murder, She Wrote," "Bewitched," "Columbo," "The Brady Bunch," and "A Different World."

Wallace — who would have turned 71 on November 1 — was diagnosed with breast cancer in 1985, leading her to become an activist on the subject. In 2007, she received the Gilda Radner Courage Award for her efforts to educate others on the disease.

She is survived by a son, Michael Hawley, who co-starred with his mother in "Muffin Top."

As news of her passing broke Saturday, Wallace's friends took to Twitter to pay their respects and celebrate her life:

Watch Wallace as Carol Kester on "The Bob Newhart Show":