
LAS VEGAS, NV - JANUARY 03: Entertainer Olivia Newton-John (L) and actress Didi Conn reunite on stage to perform "Summer Nights" at Flamingo Las Vegas on January 3, 2015 in Las Vegas, Nevada. (Photo by David Becker/WireImage)
It's a Grease reunion!
Olivia Newton-John was joined by her former costar Didi Conn during her resident show in Las Vegas on Saturday, Jan. 3 — and the two gave the audience a very special performance of 'Summer Nights'!
The duo — who played best friends Sandy and Frenchy in the 1978 musical, respectively — sang the hit song in front of a live audience at the Flamingo hotel. For the surprise performance Olivia, 66, donned a black leather jacket while Didi, 63, wore her character's signature 'Pink Ladies' satin jacket.

Olivia (left) with Didi (right) on Saturday, Jan 3.
In the classic flick, Frenchy often gives Sandy advice about her on-again, off-again relationship with Danny Zuko, portrayed by John Travolta.
Related Story: 36 Years Ago Today: 'Grease' Opened in Theaters! What We Still Love About the Movie Musical
In November, John, 60, revealed he and Olivia remain good friends thirty-six years after they played love interests in 'Grease.'

Olivia as Sandy (left) and Didi as Frenchy (right) in 'Grease.'
"We see each other about twice a year, talk about three times a year and we text every two weeks," he said in an interview.
"I love Olivia, we shared a mega success together, 'Grease' is the biggest movie musical in history and it doesn't go away," he added.