Cindy Williams, the actress who played Shirley Feeney on the classic sitcom Laverne & Shirley, has died at 75.

Williams died of a “brief illness” in Los Angeles on Wednesday, according to a statement released by her children, Zak and Emily Hudson.

“The passing of our kind, hilarious mother, Cindy Williams, has brought us insurmountable sadness that could never truly be expressed,” the statement reads, per AP. “Knowing and loving her has been our joy and privilege. She was one of a kind, beautiful, generous and possessed a brilliant sense of humor and a glittering spirit that everyone loved.”

Born in Los Angeles on August 22, 1947, Williams’ career began with TV roles in shows like Nanny and the Professor and Love, American Style.

She then broke out with roles in two of the most acclaimed Hollywood films of the 1970s: she played Laurie Henderson in George Lucas’ American Graffiti, the high school sweetheart of Ron Howard’s character, and also had a role in Francis Ford Coppola’s The Conversation.

But it was another TV appearance that would lead to her most famous role. Williams was cast as a guest star in an episode of Happy Days, along with actress Penny Marshall, as a pair of dates for Richie and Fonzie named Laverne and Shirley.

The appearance was so successful that producer Garry Marshall created a spin-off series, Laverne & Shirley. The show was became very popular, running for eight seasons, becoming America’s most-watched show in its third season.

Kicking off each week with one of TV’s most memorable intros (“One, Two, Three, Four, Five, Six, Seven, Eight! Schlemiel! Schlimazel! Hasenpfeffer Incorporated!”) the show, set in the late 1950s through the mid ’60s, followed the adventures of Laverne DeFazio (Marshall) and Shirley Feeney (Williams), best friends and roommates.

The working-class duo initially work as bottle cappers at Shotz Brewery in Milwaukee. Williams’ Shirley was the more sweet and traditional of the two, serving as counterpart to her brassier, more sarcastic best friend.

The show was a hit for many reasons, in part because it was the first time “blue-collar” women had starred in a TV series, and largely thanks to the chemistry between Williams and Marshall.

“We sort of had telepathy,” Williams said in a 2013 interview. “If we walk into a room together and if there’s something unique in the room, we’ll see it at the same time and have the same comment about it. We were always just like that.”

However, Williams eventually left Laverne & Shirley in its final season: she became pregnant with her first child which made filming difficult. After a dispute with Paramount was settled out of court, she exited the series.

“They had me working on my due date, and they couldn’t deal with it — that I needed time off to have a child,” Cindy told ET. “It just ended up I didn’t do that season of the show.”

Williams and Marshall also feuded during the final seasons of the show, although they reconciled years later.

After stepping away from showbiz for a few years to raise her child, she returned to TV in sitcoms Normal Life and Getting By.

She also had success on the stage, appearing in the national tours of many plays and musicals, and appeared on Broadway in The Drowsy Chaperone.

Williams released a memoir called Shirley, I Jest! in 2015, and reunited with Penny Marshall in an episode of the Nickelodeon sitcom Sam & Cat.

Marshall died in 2018, also at 75. Williams called her “utterly unique, a truly great talent.” “Oh what fun we had! Can’t describe how I‘ll miss her,” she told People.

David Lander, who played Squiggy in the series, died in 2020 at 73. Garry Marshall, the show’s creator as well Penny’s brother, died in 2016 at 81. Of the main cast, only Michael McKean is still alive and continues to work.