Her exact cause of death wasn't revealed, but Wallace survived a bout of breast cancer 28 years ago (she was awarded the Gilda Radner Courage Award in 2007 for her activism work).
The actress got her start on the stage, before jumping over to TV and appearing on The Bob Newhart Show as Carol Kester. She then became a game-show regular (Match Game, Hollywood Squares, and The $25,000 Pyramid) and started guest-starring on primetime shows like Murder, She Wrote and Full House.
She was publicly mourned by Simpsons producer Al Jean, who told EW, “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.”
Friends and fellow cast members, including Yeardley Smith who voices Lisa Simpson, and SiriusXM radio host Frank DeCaro, shared their grief on Twitter. Smith wrote, "Cheers to hilarious, kind, fab Marcia Wallace, who's taken her leave of us. Heaven's now a much funnier place b/c of you." (Entertainment Weekly)