Lynne Marie Stewart, ‘Pee-wee’s Playhouse,’ ‘American Graffiti’ Star Dead at 78

Lynne Marie Stewart, the actress best known for her roles in “American Graffiti,”  ”Pee-wee’s Playhouse” and “It’s Always Sunny in Philadelphia,” has died, TMZ has confirmed.

Bette Smith, Stewart’s manager tells TMZ … the actress died unexpectedly yesterday afternoon at her sister’s California home. In December, doctors found a tumor between the liver and gall bladder. Prior to the diagnosis, Stewart wrapped Ben Stiller‘s upcoming film “The Dink” … as well as kept working on “It’s Always Sunny in Philadelphia.”

“She was the most talented and funny and most honorable person I have ever known,” Smith told us of Stewart.

Cassandra Peterson, known for her iconic “Elvira” character, broke the sad news on IG, writing … “My heart is breaking upon hearing the news of my dear friend Lynne Stewart’s passing. One of the kindest, sweetest, funniest women who ever lived. The iconic Miss Yvonne of Pee-wee’s Playhouse: She’ll always be ‘the most beautiful woman in Puppetland’. 💔”

We reached out to a rep for Stewart for more info … so far, no word back.

As Cassandra noted, Stewart played Miss Yvonne, The Most Beautiful Woman in Puppetland, on “Pee-wee’s Playhouse” from 1986 to 1990 … and she appeared in several other ‘Pee-wee’ titles, including “Pee-wee’s Big Adventure” and “Big Top Pee-wee.”

The actress also appeared in the iconic George Lucas film “American Graffiti” and the Arnold Schwarzenegger classic, “The Running Man.”

Stewart’s more recent fan-favorite role was as Charlie Kelly’s mother Bonnie, in “It’s Always Sunny in Philadelphia.”

She was 78.