Thea White, who voiced Muriel on the cartoon Courage the Cowardly Dog, died Friday at age 81.

Her brother John Zitzner announced the sad news on Facebook, writing in another post that White died after battling liver cancer, which she was diagnosed with months ago. He said she underwent two surgeries in July before dying "peacefully" Friday morning at the Cleveland Clinic in Ohio.

In his initial post, Zitzner shared an upbeat video message from White before her surgery.

White got her start in theater but was best known for voicing Muriel, the elderly woman who owned the fearful pink dog along with her grumpy husband in the Cartoon Network animated series. She voiced the character from 1999 to 2002 and reprised the role in various shorts and games. She also voiced Aunt Margaret in the 2011 movie Scooby-Doo! Legend of the Phantosaur. Zitzner also said in his Facebook post that White was "looking forward to seeing" the upcoming film Straight Outta Nowhere: Scooby-Doo! Meets Courage the Cowardly Dog, which features her as Muriel once again.

Born Thea Ruth Zitzner on June 16, 1940, in Newark, N.J., she studied acting at the Royal Academy of Dramatic Art in London and at the American Theatre Wing in New York, according to The Hollywood Reporter. She got her start as Marlene Dietrich's personal assistant, a gig she landed via her future husband Andy White, who played the drums for Dietrich's concert act. After their marriage, White became a librarian but later decided to audition for Courage the Cowardly Dog, as the show was looking for someone with a Scottish accent to play Muriel, and White's husband was Scottish.

In a February interview, White revealed she had her own dog named Courage and said it was "so much fun" working on the show. She also said she was "surprised by how many young kids loved being scared."

"I got a fan letter once from a little boy who was 7 years old and he wrote me and he said, 'Could you please tell them to make more Courage the Cowardly Dog, and please tell them to make it scarier and scarier?'" the actress recalled.

White is survived by her two brothers and "countless" other family members, Zitzner wrote on Facebook. Her husband Andy, who also recorded with the Beatles in addition to playing drums for Dietrich, died in 2015.

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