Grease is the word... again
It is nearly 35 years since Sandy and Danny danced their way into the nation's hearts in hit film Grease, but John Travolta and Olivia Newton-John have finally shimmied their way back into the recording studio.
The clue to what they are doing now is in the video for the duo's new single, I Think You Might Like It, which imagines the Grease characters getting back together for a Christmas celebration.
The single is written by John Farrar, whose last song for the couple was You're The One That I Want, which is the fifth best-selling single of all time in the UK.
When Newton-John texted Travolta to tell him of the single's success, his response was immediate.
"I texted her back and said let's do a Christmas song," he tells the BBC.
But instead of one song, they decided to do a whole album and headed into the studio in July to record it.
"The chemistry was right where we left it" says Travolta, who chose songs that "allowed us to be the voice quality that we were in Grease".
Newton-John decorated the studio in Christmas decorations, and she says: "John bought reindeer antlers and Santa hats so we got right in the spirit".
The album, a compilation of Christmas classics, also features a few of Travolta's famous friends.
"They all knew my son. When I called Barbra Streisand, she didn't hesitate at all," he says.
"Neither did James Taylor, Tony Bennett, Kenny G or Chick Correa. All said yes immediately. Probably the most touching thing of all is the lack of hesitation. "
Newton-John was keen to get Cliff Richard on board.
"It was really important to me that he was a part of it, as he was so important to my career and starting me off in the UK," she says.
"It's a project that we're hoping turns into a perennial one, that can continue to raise money for these causes year after year. A gift that keeps on giving."
And the burning question - now they've reignited the Grease partnership, are they tempted to make another film?
"Paramount is relentless about trying to get a third one up but there's just such magic to that first one that it's hard to compete with that," says Travolta.
The pandemonium that surrounded them at the height of Grease's fame saw barriers strained, girls fainting and Travolta being rushed with a police escort through crowds, as he ran a gauntlet of grabbing hands.
The occasion was the UK premiere of Grease in July 1978 - and the star remembers it like it was yesterday,
"I have a phenomenal memory of the intensity," he says.
"Our limo rocked, the ceiling started to cave in because of the fans, and the police couldn't control them.
"I don't know what it compares to - other than when The Beatles came to the US for the first time. We were getting that kind of reaction in the UK."
Archive footage of the event proves he is not exaggerating (the Australian premiere was even more frenzied).
Fans had fallen in love with Sandy and Danny before the film even came out, thanks to the success of the single, You're The One That I Want, which topped the charts around the world in May.
Grease told the story of the couple's summer romance at Rydell High School, complete with quiffs and tight trousers. But it ended with the characters flying into the sunset in the famous Greased Lightning car.
So what happened to Sandy and Danny after the credits rolled? Are they still together like shoo bop shoo-wadda wadda yipitty boom de boom?
"In our minds they absolutely are" says Travolta. "You'll never see Danny and Sandy apart from each other".
Except, as Olivia Newton-John points out: "Danny's gone from the flying car to the aeroplane."
But the video, has left some critics scratching their heads.
Courtney Hazlett from NBC Today. wrote: "How the video and song - which features Travolta descending from a private jet, contrived two-stepping, and lots of pasted-on smiles and melodramatic reunions - continues the story told in You're the One That I Want is something of a mystery."
The Washington Post suggests watching the video but then, "wash out your brain and refill it with more pleasant images of Travolta and ONJ".
But it is not all negative. E Online says the clip proves "that Sandy and Danny haven't lost their groove, all these years later".
The director, Rav Holly, explained to OMG! that the whole project was funded by Travolta and Newton-John and that the budget was limited,
To keep costs down they filmed at the Ocala airport, behind the gates of Travolta's exclusive community of Jumbolair. where nearly every resident has a private jet.
The result was scenes of Travolta and Newton-John toe-tapping on the Ocala air strip.
But despite them rekindling their old chemistry, it seems that they are reluctant to bring Sandy and Danny into the 21st Century.
He concludes: "I almost feel like we have to do a Christmas movie or some other movie that reminds you of Sandy and Danny but that isn't them in order to do it correctly."
So die-hard fans will have to content themselves with re-runs of Grease, but with the popularity of the film showing no sign of waning, it should be hitting the small screen for many years to come.