Watch Catherine Zeta-Jones Explain TikTok to Michael Douglas (Exclusive)

The 75-year-old was not familiar with the popular app.

Catherine Zeta-Jones and Michael Douglas are having fun in quarantine! The couple is happy to have their two children, Dylan, 19, and Carys, 17, home amid the ongoing coronavirus pandemic. 

"I must say as crazy and as unchartered as these waters are, it has been wonderful having these kids home, and I applaud them for being so contentious with their schoolwork and really jumping up to the plate," Zeta-Jones, 50, tells ET's Kevin Frazier. 

The family has been spending their downtime playing music together. 

"We bought a guitar," the Chicago star reveals. "I play a bit of piano, my daughter plays piano, we sing. Downstairs, there's a drum kit. We bought four acoustic guitars, electric guitar, drum kit and so it's a musical household. There's always singing in the back room. I digged out the karaoke machine."

But when Frazier suggests that the couple try out TikTok, Zeta-Jones has to step in to explain the app to her 75-year-old husband. 

"OK, TikTok. TikTok is a one-minute video online social media," she tells him. "Just say, 'I'm not into TikTok.'"

"I'm not into TikTok right now," Douglas obediently replies. 

"There's only so much Michael Douglas can fit into a minute," Zeta-Jones quips. "We're used to a feature length, two-and-a-half hour."

That doesn't mean that Douglas wouldn't have plenty of top-notch material for a TikTok. 

"Michael was trying to moonwalk last night at dinner, but he was going forward not backwards," Zeta-Jones reveals. "It was memorable because I’ve never seen anyone moonwalk with the arms going backwards but his body thrusting forward. It was really... we need to work on that."

"I was so cocky. This is not that hard," Douglas agrees. "Then Catherine said, 'Honey, you’re going forward. You’re not going backward.'" 

In addition to their family fun, the pair are also supporting the Motion Picture Television Fund ahead of the organization's 100th anniversary next year. 

"We are also proud of our industry, because I think we are the only industry that has an organization that takes care of their own, so not just actors -- I am talking about screenwriters, I am talking about costumers, I am talking about construction people, anybody who works in the movie business can rely on the Motion Picture Television Fund to help them out," Douglas notes.  

The “We All Play Our Part: A Benefit for MPTF” will take place on Friday, May 15.