Marcia Wallace, the Bob Newhart Show vet who also voiced The Simpsons‘ school marm Mrs. Krabappel, has died. She was 70 years old.

Simpsons executive producer Al Jean confirmed the actress’ death to several media outlets on Saturday. Wallace’s friend Cathryn Michon told our sister site Deadline that Wallace, who had battled breast cancer in the past, died from complications of the disease.

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“I was tremendously saddened to learn this morning of the passing of the brilliant and gracious Marcia Wallace,” Jean said in a statement. “She was beloved by all at The Simpsons and we intend to retire her irreplaceable character.”

Jean added that Mrs. Krabappel is not the character the series is planning to kill off later this season.

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Wallace, who had won an Emmy for voicing the cynical Springfield teacher in a 1992 episode of the Fox animated comedy. Early in her career, she was known for playing The Bob Newhart Show‘s receptionist Carol.

Her long career includes appearances on Murphy Brown, Full House, 7th Heaven and The Young and the Restless.