Famous Friends Remember Olivia Newton-John: 'My First Real Crush As A Kid'

Actress Olivia Newton-John passed away at the age of 73 on Monday.

Although a rep did not disclose a cause of death, they did say that Olivia had lost her 30-year battle with metastatic breast cancer. She had first been diagnosed in 1992 and went into remission, but it returned in 2013 and 2017.

Plenty of famous friends have been taking to social media to express their condolences, starting with "Grease" costar John Travolta.

The 68-year-old actor took to Instagram to remember his "Grease" costar. “My dearest Olivia, you made all of our lives so much better," he wrote. "Your impact was incredible. I love you so much.”

“We will see you down the road and we will all be together again,” he continued. “Yours from the first moment I saw you and forever! Your Danny, your John!”

"Seinfeld" star Jason Alexander tweeted, "I never met Olivia Newton-John. I was only a hopelessly devoted fan. I’m told she was one of the dearest and kindest people. My sympathy to all her loved ones. #RIPOliviaNewtonJohn."

"Now and Forever" singer Richard Marx tweeted, "My heart is broken. Rest now, sweet friend. You were as kind and loving a person as there’s ever been. I’ll miss you every day. ?."

“Community” star Yvette Nicole Brown retweeted a tweet from January 12, 2012, where she tweeted, "Just realized my last tweet was cut off. To be succinct...I MET OLIVIA NEWTON-JOHN! :) #MustCalmDownNow."

"A little over twelve years ago, I geeked out at meeting one of my all time faves when she visited the set of Community," she recalled. "#OliviaNewtonJohn’s hairstylist worked on our show. I think she was there to get a haircut in our hair trailer. ❤️."

"Star Trek" actor George Takei tweeted, "We have lost a great, iconic artist in Olivia Newton-John, gone too soon from us at age 73. I trust she is now in the great Xanadu beyond. Know that we are forever hopelessly devoted to you, Olivia. Rest in song and mirth."

"Bring It On" actress Gabrielle Union said that "Grease" was her "1 movie of all time" and made her a lifelong Olivia Newton-John fan. "Me and my sister watched Xanadu more times than I could count," she continued. "Sending so much love and prayers to a real gift of a woman and talent. #RIPOliviaNewtonJohn ????????."

Comedian Dane Cook tweeted, "RIP Olivia Newton-John. Thank you so much for wonderful music and fun memories."

He later added, "When my mom was fighting cancer, even though some days were brutal, she was never not funny. Her strength & humor I think of often. It’s why I love standup, the ability to find ways to laugh when it feels like too much & honoring my mother by helping others do the same."

"Guardians of the Galaxy" director James Gunn tweeted, "Really sad to hear about the passing of Olivia Newton-John. My first real crush as a kid. I loved Grease & her music & I coincidentally also bought & lived in for a while the wonderful home she built in Malibu. May she Rest In Peace. ❤️."

The first Deaf Academy Award-winning actress for 1986's "Children of a Lesser God," Marlee Matlin, tweeted, "I am SO saddened at the news of the passing of Olivia Newton-John. I remember being so star struck when I met her at my first Hollywood gathering for Paramount. She was the sweetest and brightest light and I loved getting to know her on 'It's My Party.' RIP dear, sweet Olivia."