The 'Laverne & Shirley' star - who was the younger sister of the late writer, producer, and director Garry Marshall - passed away on Monday (17.12.18) after suffering complications from diabetes at the age of 75.
And several celebrities including Rosie - who shared the YouTube video for a K-Mart commercial she starred in alongside Penny - have already taken to social media to pay their respects.
Posting the video link on Twitter, the 56-year-old comedian wrote: ''simply heartbroken #ripPENNY (sic)''
Whilst actress Busy Philipps tweeted: ''Oh Penny Marshall. Rest In Peace and thank you for everything. (sic)''
Melissa Joan Hart took to Instagram to mourn the loss of the 'A League of Their Own' director, as she praised Penny for being a ''special role model'' to female comedians.
She captioned an old picture of Penny: ''Heartbroken to learn that #PennyMarshall has passed away!! The Marshall family holds a special place in my heart for being so kind and creative and encouraging to other artists. But she was a special role model for female comedians like myself. #RIP #ThankYou (sic)''
'Stranger Things' actor Sean Astin also tweeted his condolences to Penny's family and friends, as he said he was thinking of her ''brilliant moments'' whilst sitting on a sit-com set himself.
He wrote: ''I got to stay up late-after Happy Days-2 watch Laverne & Shirley. So sad 2 learn that Penny Marshall has passed. Sitting on a sit-com set 40 years later, thinking about milk & pepsi, rodeo-doh-doh-doh & so many of her brilliant moments. Love to her family, friends & our town... (sic)''
Shortly after news of her passing broke, Penny's family released a brief statement saying they were ''heartbroken'' by the loss.
They said: ''Our family is heartbroken over the passing of Penny Marshall.''
What's new in the music world this week?
'Sounds of Silence' was released on this day (January 17th) in 1966.
Listen to Alex Bayly performing 'Animal'.
Two weeks ahead of Independent Venue Week, Dry Cleaning made 'Britain's Best Small Venue 2015' (NME) the second port of call on their 2020 tour.
'Leave Home' was released on this day (January 10th) in 1977.
For their last gig of the year, The Libertines came back to their adopted hometown of Margate to finish off their latest tour.
Celebrating the birthday of David Bowie with his most legendary songs.
Kevin Clash is one of America's most popular performers, and yet he's rarely recognised in...
Tarzan the Ape Man gets the Disney treatment this year. For some classic characters...
With a cryptic title like Beautiful Girls, one starts to wonder to whom this film...