ET's Matt Cohen met with the veteran actress on Monday to discuss the over 500 items that she's decided to put up for auction next month to benefit the cancer treatment center bearing her name in Australia. While on hand, she revealed some little-known facts about the memorabilia, including that she had to be literally sewn into the black pants in the film's finale, following Sandy's transformation, because the zipper was broken.
"They had to stitch me into them when I had to shoot," she says while standing alongside the item at Julien's Auctions in Beverly Hills, California. "The zipper's still broken, but they're fabulous. They're just gorgeous."
The 71-year-old actress also shared that, while shooting the musical's big ending, they were experiencing some sweltering temperatures in Los Angeles at the time, making filming the scene a challenge.
"It was pretty comfortable except it was incredibly hot," she tells ET, later adding, "They were having a heat wave, so I obviously had to take this jacket off in between takes because it was very, very hot. So, I have sweated in this jacket."
Another item up for auction is Newton-John's own Pink Lady jacket. As fans of the film know, Sandy was never inducted into the film's girl gang, but when production wrapped, they made Newton-John an honorary member and presented her with her own jacket, which is even embroidered with her character's name.
"I wanted to be a Pink Lady, I wanted to be accepted by them," Newton-John says of her character in the film "But, of course, I wasn't a part of the team in the end. So, the crew, at the end of filming, presented me with my own Pink Lady jacket, so I'd feel part of it."
Since the 1990s, the actress has battled cancer three times and become a fierce advocate for fellow survivors. Last year, she was diagnosed with a tumor in her lower back and underwent treatment in the facility she helped create, the Olivia Newton-John Cancer Wellness & Research Centre in Victoria, Australia, which will receive the proceeds from the auction.
"I was in a lot of pain and I ended up being a patient on my 70th birthday in my hospital," she shares. "Which was really amazing. I mean, it sounds strange to say, but it was really a gift because I got to experience what I helped create."
Newton-John added that the experience motivated her to work as hard as ever to help provide the treatment center with support.
"The staff were incredible and the place was beautiful and so this makes it even more inspirational for me to raise more money," she explains. "So, we can do more research and see an end to cancer in my lifetime, which is my dream."
The auction of Newton-John's prized Grease items will take place at Julien's Auctions in Beverly Hills on Nov. 2 and at juliensauctions.com.