The Knots Landing star took to Instagram on Sunday to share how she was used as a model for the character who was made famous by Olivia Newton-John in the 1978 big screen adaptation of the stage show. Narrating videos of herself in Sandy's two signature looks from the musical, Donna said, "Did you know that I went to school with Jim Jacobs? Jim Jacobs, who wrote Grease. Jim Jacobs, who used me as his model for Sandy." Jim wrote the stage musical with Warren Casey based on his time at high school in Chicago.