Let's get physical, because on these summer nights, you're the one that I want. So it goes with Olivia Newton-John (59 today), the cultural epicenter of the late '70s and early '80s. First she stars in "Grease," the film beloved by the ladies the way we guys overdo it for "Star Wars." Then in 1982 Olivia shocked the world with "Let's Get Physical," which spent ten weeks at number one. Who took Olivia's place as the starring blonde in the appropriately titled "Grease 2"?

Barbara Bach

Kim Catrall

Melanie Griffith

Michelle Pfieffer

Jenna Elfman