Update Sunday 9:00 a.m.: Wallace's son Michael Hawley tells KPCC she died of complications from pneumonia.
Update 3:59 p.m. Saturday: Marcia Wallace, the voice of Bart Simpson's teacher Edna Krabappel on "The Simpsons," has died. She was 70.
"Simpsons" executive producer Al Jean said in a statement Saturday that her death is a terrible loss. He says Wallace's "irreplaceable character," the fourth-grade teacher who has to deal with Bart Simpson's constant antics, would be retired from the show.
"For a few episodes, we have lines she recorded, which I'm sure she would want us to use and stay in, and then we'll retire the character and Bart will have a different teacher," Jean told KPCC. "I don't see anybody who could replace somebody as unique and terrific as her."
"It's terrible for everyone involved with the show," Jean said. "She was just such a wonderful person, and what you saw was what you got. She was really genuine and really funny."
She started with "The Simpsons" in the show's first season.
"She was one of those people you'd love writing a line for her, because she'd make it a million times funnier when she delivered it," Jean said. "There was a line, where it was in the future. Bart was now 25, and he was on a date with her. And he [says], 'A date with my teacher? This is pretty weird.' And then she just goes, 'Want it to get weirder?' And the way she read it was one of the biggest laughs in the history of the show."
When asked what made Wallace so special in her role on "The Simpsons," Jean said, "You would both laugh and then have sympathy for the character at the same time."
She appeared in 177 episodes of "The Simpsons," winning an Emmy for her voice work. She brought to life the school-weary Edna Krabappel, a teacher who punctuated her own punchlines with a signature laugh: "Ha!"
The feisty redhead TV actress' credits ranged from playing wise-cracking receptionist Carol on 1970s sitcom "The Bob Newhart Show" to appearances on Candice Bergen's "Murphy Brown."
Cathryn Michon, Wallace's friend for 15 years, directed Wallace in her last film, the romantic comedy "Muffin Top: A Love Story," in which she played herself.
"She just took everything that was negative that got thrown at her and turned it into something positive, because that's just who she was," Michon told KPCC.
Wallace was a longtime advocate for breast cancer survivors and awareness. She battled breast cancer herself, and she also suffered from vertigo, said Michon.
A native of Iowa, Wallace was a fixture on American television for decades, from her appearances on "The Merv Griffin Show" to jokey game shows such as "Hollywood Squares" and "Match Game."
To many, Wallace's work as receptionist Carol Kester on "The Bob Newhart Show" defined her career, as her short red hair, wide smile, and a gift for comedic timing helped the show mine the 1970s dating scene for laughs.
She brought a resilient sense of humor to a character who was often tested by uniquely odd circumstances, from dating a patient of her psychologist boss to falling for the man who removed a butterfly tattoo from her posterior.
Wallace lived in Los Angeles. She was a national board member of SAG-AFTRA.
Some clips of Mrs. Krabappel in action:
This story has been updated.