By People Staff
May 04, 2010 12:00 AM
Sipa; FOX

Don’t look for Sandra Dee on Tuesday’s episode of Glee.

For her guest appearance on FOX’s hit musical comedy, Olivia Newton-John will show off “the dark side of myself,” the Grease star says. “I’m not terribly nice. It’s a mixture of mean and diva. I don’t believe I have this side but it’s amazing how easy it came out!”

Playing herself, the singer calls up McKinley High’s ruthless cheerleading coach Sue Sylvester after spotting a remake of her “Physical” video that Sylvester posted online. The two then join forces to improve on the project.

“It was really fun to see the set. They redid it exactly the way it was in the original video!” says Newton-John, 61, who put in a 12-hour day with Jane Lynch. With one exception: “We have our own version of the headband.”

“Just the experience of being dressed up in exercise gear and dancing and singing with Jane was funny,” continues Newton-John, who gave her costar Lluvia skin products as a thank you at the end of the shoot. “I’ve never laughed so hard, my jaw was sore by the time I left.”

The singer admits that she wasn’t a true “gleek” until recently, and growing up in Australia she was never a show choir kind of girl.

“I was part of the drama club. But I avoided choir because they always wanted me to do solos so I tried to get out of it,” says Newton-John, laughing. “I was shy.” –Michelle TanSipa; FOX