Sandra "Sandy" Olsson is one of the main characters Grease. Sandy and her family moved to America from Australia, after summer vacation. She and Michael Carrington (from Grease 2) are cousins. She is also the girlfriend to Danny Zuko. Even though didn't become a member of the Pink Ladies, because Rizzo, the leader, thought she was "too pure to be pink," at the end of the movie she is accepted as a female greaser. Sandy is portrayed by Olivia Newton-John in the 1978 film, by Julianne Hough in the 2016 performance.
Sandy is an extremely beautiful young woman with blonde hair, blue eyes, and a fair complexion. Throughout the majority of the movie, Sandy wears very feminine clothes, such as a skirt-and-sweater set that are always in pastel colors such as yellow, pink, etc. At the National Dance-Off, she is wearing a white dress and white high heels (and, though only seen briefly, white panties). However, at the end of the movie, Sandy undergoes a beauty makeover to surprise Danny, so she appears wearing "female greaser" attire.
Sandy is very good-natured, speaks kindly to everyone, and has a very soft and sweet personality. She was deemed "too pure" in contrast to the other Pink Ladies by Rizzo. While at a pajama party at Frenchy's house, a puff from a cigarette and a sip of dessert wine - along with the sight of blood after Frenchy pierced her ear - made her sick. She is trusting, a bit naïve, and can be easily hurt. She finally gained confidence and changed her "pure" image into a rebel-like appearance and attitude to be with Danny, who at the end of the school year had lettered in track, to soften his image to be with her.
During the summer of 1958, teenager Danny Zuko meets Sandy Olsson at the beach and fall in love. When the summer comes to an end, Sandy, who is going back to Australia, frets that they may never see each other again, but Danny tells her that their love is "only the beginning." Afterward, the film moves to the start of the new school year at Rydell High School. After her parents decide to move to America, Sandy enrolls at Rydell and Frenchy befriends her. Oblivious to each other's presence at school, Danny and Sandy tell their respective groups the accounts of events during the pair's brief romance (Summer Nights). Upon learning Danny Zuko was Sandy's summertime sweetheart, Rizzo arranged for the two to reunite, but Danny was under pressure to maintain his bad-boy attitude in front of his buddies, upsetting Sandy. She runs away and cries.
Frenchy decides to cheer Sandy up by having her join her and the girls at a pajama party at her house, but Sandy fell ill from trying a cigarette and having a sip of imported dessert wine. To top it off, she got one of her ears pierced by Frenchy, saw the blood, and throws up. After the T-Birds arrived outside of Frenchy's house, they left with Rizzo, Sandy reflected on her feelings for Danny (Hopelessly Devoted to You).
Some time later, at the Frosty Palace, Danny tried to apologize: "It was me, but it wasn't me." She rebuffed him - she was with Tom Chisum, one of the jocks whom Sandy describes as "a simple person." Danny remarks: "Too bad his brains are in his biceps." Danny also denies jealousy, and says he can "run circles around those jerks." Sandy answers: "I'll believe that when I see it." Seeing that Sandy likes jocks, Danny asks Coach Calhoun to help him with athletics and becomes a runner. He saw Sandy with Tom, and picked up speed jumping the hurdles, but he overdid it and took a header when jumping over a hurdle. She came running to him to see if he was all right, showing she still cared for him. He half-heartedly gave her the `silent treatment', but she tricked him into talking, finally, and they decided to have another chance at being together. They attempted to go on a date at the Frosty Palace, but the Pink Ladies and T-Birds crashed it. After leaving, Rizzo and Kenickie have a fight. The school dance arrived, broadcasted live on national television, with DJ Vince Fontaine and Johnny Casino & The Gamblers. Danny and Sandy arrive together. During the dance contest, Sonny grabs Sandy and takes her away from Danny. Cha-Cha grabs Danny's arms and they danced together to Hand Jive. Sandy left, and Danny and Cha-Cha won the dance-off.
Later, Danny tried to make it up to Sandy by taking her to a drive-in. She went to be with him and watch the movie, and Danny gives Sandy his ring. He asked her to go steady, she said yes, and declared that he truly respected her. Afterward, Danny tried to make out with Sandy, but she slammed the door on him, threw his ring in his face and ran off. Danny was heartbroken (Sandy Song), and believed the two of them belonged together. Sandy knew Rizzo looked down on her for being "too pure," but that didn't stop her from offering to help when it was rumored that Rizzo was "knocked up." Rizzo initially balked at the offer, stating that she could take care of herself, and anybody else that came her way. Saddened, Sandy was about to leave, when Rizzo called to her, and sincerely thanked her.
The Thunder Road race arrived, Sandy watches from afar, and after Danny won, she concluded she still loved him, but came to believe her goody-two-shoes image didn't sit well in America (Look At Me, I'm Sandra Dee (reprise). She asks Frenchie to help her. Some time later, on the last day of school, the class celebrated their graduation at the carnival on the school grounds. Danny had become a jock and is wearing a letterman sweater, but was shocked when Sandy appeared dressed in a black leather jacket, an off-the-shoulder top, black pants and belt, red high heels, her hair teased, makeup, and hoop earrings. In song, the two admitted they loved each other (You're The One That I Want). The film ended with Danny and Sandy departing in the totally tricked-out Greased Lightning car together, with Sandy waving goodbye to their friends (We Go Together).