After the sudden passing of Cindy Williams, known for her role as Shirley from the "Happy Days" spin-off "Laverne & Shirley," two of the original show's biggest stars are remembering her for not only the work they produced together, but also the friendships they developed.

Ron Howard, who originally starred alongside Williams in the 1973 film "American Graffiti," remembers the actress as having "big sister energy," despite playing love-interests in the film.

"She was 24 and I was 18," Howard told People magazine. "I had my first kissing scenes with her, but they weren't very romantic because she knew that she had this nervous kid on her hands and she had to take charge of the situation…And so she was like, 'Here's how we got to kiss for the camera. Here's what we have to do.' She's always had almost a big sister energy around me."

Howard, 68, had recently reconnected with Williams last year, which only magnified the impact of losing her.

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"I'm shocked because I hadn't seen her for years and years," he said.

"We connected at an event in Palm Springs [California] last year, and I was just so taken by how her intelligence, energy, and sense of humor...was still in high gear. And so it's really a shock to imagine that spark is gone," Howard continued.

"We wound up over a period of about five years working together a lot, being cast in other comedies, in dramas," Howard shared of his relationship with Williams. "We had terrific acting chemistry, but she always treated me like the kid."

Williams family shared on Monday that the 75-year-old had died following a brief illness.

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Henry Winkler, 77, shared similar sentiments as Howard, telling The Hollywood Reporter, "Cindy has been my friend and professional colleague since I met her on the set of ‘Happy Days’ in 1975. Not once have I ever been in her presence when she wasn’t gracious, thoughtful and kind. Cindy’s talent was limitless. There was not a genre she could not conquer. I am so glad I knew her."

In the wake of her passing, several other Hollywood stars have voiced their sadness for the loss of Williams.

"Laverne & Shirley" co-star Michael McKean paid tribute to Williams on his Twitter, recounting a memory with the actress.

"Cindy scoots by me to make her entrance and with a glorious grin, says: 'Show's cookin'!'. Amen. Thank you, Cindy," he wrote in part.

"Cindy was AMAZING," Jamie Lee Curtis captioned a photo of Williams on her Instagram. "Such a great, natural comedian. So wide open. Such a sad loss."

Actress Rosario Dawson retweeted a scene from "Laverne & Shirley," writing, "Singing this song with so much gratitude for both of you ladies. Absolute gems. United again…Rest in Paradise Cindy Williams." Penny Marshall, who played Laverne in the iconic show, predeceased Williams in 2018.

"Seinfeld" actor Jason Alexander shared his remorse to Twitter, explaining that while he did not know Williams personally, he adored her work.

"I pray she had a good life and send my sympathy to those who knew and loved her," he wrote.

Katie Couric also shared her condolences tweeting, "Rest in Peace, Cindy Williams" alongside a red heart emoji.