Sandra Dee "Sandy" Olsson is one of the main characters in 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. She didn't become a member of the Pink Ladies because Rizzo, the leader thinks she's "too pure." Sandy is portrayed by Olivia Newton-John in the 1978 film, by Julianne Hough in the 2016 performance, by Danielle Hope in the 2017 UK tour and by Skye Hunt in the 2017 version performance (alongside her co-star and singer, Nathan Parker whom played Hunt's love interest).
Sandy is a very pretty girl, with blonde hair, blue eyes and fair skin. Throughout the majority of the movie, Sandy wears very feminine clothes, such as a skirt-and-sweater set that are always in light colors such as yellow, pink, etc. However, at the end of the movie, Sandy undergoes a beauty makeover to surprise Danny.
Sandy is very good-natured, speaks kindly to everyone, and is very soft. She was deemed "too pure" in contrast to the other Pink Ladies by Rizzo. At Frenchy's slumber party, the sight of blood - coupled with a puff from a cigarette and a sip of dessert wine - made her sick. She is trusting, a bit naïve, and can be easily hurt. She finally gained confidence and changed her "pure" image, and adopted a fiercer, sexier appearance and attitude to be with Danny, who at the end of the school year had lettered in track, to soften his image for her.
During the summer of 1958, local boy Danny Zuko and vacationing Sandy Olsson meet 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 seniors' term at Rydell High School. After her parents decide to move to America. Sandy enrolls at Rydell and befriends Frenchy. 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 pals, upsetting Sandy, and Sandy runs away and cries.
Later, Frenchy invited the girls to a pajama party, but Sandy fell ill from trying a cigarette and having a sip of imported dessert wine. To top it off, she got her ear pierced by Frenchy, saw the blood, and became sick and throws up. After the T-Birds crashed the party and left with Rizzo, Sandy reflected on her feelings for Danny (Hopelessly Devoted to You). Some time later, at a burger joint, Danny tried to apologize: "It was me but it wasn't me"...etc, she rebuffed him - she was with Tom Chisum, whom 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." Danny actually did that, finally choosing Track and Field. 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, with Rizzo and Kenickie having a fight. The school dance arrived, broadcasted live on television, and Danny and Sandy came together. During the dance, a perhaps drunk Sonny cut in, pulling Sandy away from Danny. Cha-Cha DiGregorio, who once dated Danny, took that as her cue, and performed together to Hand Jive. Sandy left just before Danny and Cha-Cha won a 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 and threw his ring in his face and ran off. Danny was heartbroken (Sandy Song), and believed the two of the 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 he won, she concluded she still loved Danny, but came to believe her goody-two-shoes attitude didn't sit well in America (Look At Me, I'm Sandra Dee (reprise). She asks Frenchy 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, but was shocked when Sandy appeared, dressed in black - a leather jacket, tight satin pants, an off-the-shoulder top, red high heels, her hair teased, makeup, hoop earrings, and a cigarette in her hand. In song, the two admitted they loved each other and reunited (You're The One That I Want). The film ended with Danny and Sandy departing in the totally tricked-out Greased Lightning car together, which then took flight, and the pair waved goodbye to their friends (We Go Together).