Lynne Marie Stewart, who played Pee-wee Herman’s perky, bouffant-wigged neighbor, Miss Yvonne, in the 1980s children’s television series “Pee-wee’s Playhouse” and the sweet, timorous mother of one of the main characters in “It’s Always Sunny in Philadelphia,” died on Friday in Los Angeles. She was 78.
The cause of her death, at her sister’s home, was cancer, said her manager, Bette Smith. Her doctors found a tumor shortly after Ms. Stewart finished filming a movie called “The Dink,” a comedy starring Jake Johnson and Ben Stiller, in December, Ms. Smith said.
Ms. Stewart played a variety of characters in a career that spanned six decades, and had nearly 150 credits as a screen, stage and voice actress starting in 1971, according to IMDb, the entertainment database.
But she was perhaps best known for her role as Miss Yvonne, or the “most beautiful woman in Puppetland,” in “Pee-wee’s Playhouse,” which ran for five seasons on Saturday mornings on CBS.
She was a fixture on the show as Pee-wee Herman’s extravagant neighbor with creative hairdos and a chipper personality.
With its whimsical and slyly subversive sense of humor, the show swiftly attracted an audience beyond its core demographic of preadolescent children, and Ms. Stewart and other members of its cast embraced its anarchic and surreal spirit of make-believe.
“I would go on commercial interviews and be labeled as a woman over 40,” Ms. Stewart told The New York Times in 2004. “Then I would go to my day job” on the “Pee-wee’s Playhouse” set, “where I got to be a storybook princess.”
Lynne Marie Stewart was born in Lynwood, Calif., on Dec. 14, 1946. Her sister, Gayle Stewart, is her only immediate survivor.
Ms. Stewart developed an interest in acting while attending Beverly Hills High School and went on to study theater arts at Los Angeles City College. She was still attending Los Angeles City College when she befriended another student and aspiring actress, Cindy Williams.
As she established herself as a working performer, Ms. Stewart would appear with Ms. Williams in seven episodes of the sitcom “Laverne & Shirley” and performed onstage with her in New Jersey in a production of “The Female Odd Couple.”
In the 1970s, Ms. Stewart joined the Groundlings, the Los Angeles improvisational theater company that has trained several well-known comedic performers. It was there that she befriended Paul Reubens, who created the Pee-wee Herman character.
He recruited her to perform as Miss Yvonne in “The Pee-wee Herman Show,” which was billed as a “live onstage TV pilot.” She reprised the role in a national tour and a 1981 HBO special, as well as in “Pee-wee’s Playhouse” and a 2010 Broadway revival.
She also appeared with Mr. Reubens in three Pee-wee Herman films, though not as Miss Yvonne: “Pee-wee’s Big Adventure” (1985), “Big Top Pee-wee” (1988) and “Pee-wee’s Big Holiday” (2016).
Starting in 2005, she had a recurring role on “It’s Always Sunny in Philadelphia” as Bonnie Kelly, the good-natured, if high-strung, mother of Charlie Day’s character, Charlie Kelly.
She often performed with Sandy Martin, who plays the mother of Rob McElhenney’s character, Mac, as a couple of dysfunctional mothers and odd-couple roommates.
Ms. Stewart was a proud alumna of the Groundlings and stayed involved with the organization long after she had moved on to film and television roles. Her time with the troupe, she said, prepared for the success she found late in her career on “It’s Always Sunny,” the longest-running live-action sitcom in U.S. history.
“Besides characters, you could work on the character of yourself,” she told The Hollywood Reporter in 2013.
When she was cast as Bonnie, she said, “I came in with the confidence of knowing that I can improvise as myself, and that was straight from the Groundlings.”
