New York (CNN) -- Writers Nora and Delia Ephron know their way around a punch line.
They've proven themselves by crafting good dialogue for films -- both on their own (Nora's "Julie & Julia") and together ("You've Got Mail"). But the latest dialogue for the siblings is on stage.
They have put together a production fashioned around Ilene Beckerman's best-selling book "Love, Loss and What I Wore."
"I started reading it and I thought, 'Oh, what a great idea, to tell your life story through ... the clothes you were wearing,' " Nora Ephron says.
"I had such envy of the idea, even though if I wrote a book like that it would be called 'Love, Loss and What I Ate.' But I thought what a brilliant idea and so now we've kidnapped it and here it is."
"It makes you think about your own life," adds Delia Ephron.
The Ephrons' stage version includes portions of Beckerman's book, with the rest of the show based on interviews done by the sisters.
The show has a rotating cast that has included Rosie O'Donnell, Tyne Daly and "Glee's" Jane Lynch. It was scheduled for a limited run but will play on into the new year because of its success.
While some of the stories in the play are personal to the Ephrons, tales told by their friends found their way onto the stage as well.
"Each story is true, everything on that stage is true. Everything was said, everything actually happened," says Delia. "So I think that's why it has power."
The Ephron sisters' gift for writing and comic timing may very well be inherited.
Their parents were Henry and Phoebe Ephron, whose screenwriting resume includes the films "Carousel," "Desk Set" and "There's No Business Like Show Business." While these works live on through movie rentals and classic film channels, perhaps the elder Ephrons' true legacy is their daughters.
"They were funny and they believed that everything was copy," says Nora Ephron. "They believed that anything in life could be turned into a story, which is really the first rule of humor."
"I just remember my father at the dinner table. There are four sisters, and my parents," recalls Delia Ephron. "And every time we said something that my father thought was memorable, he'd scream: 'That's a great line -- write it down.' "
But their childhoods weren't all fun and games, say the sisters, particularly since family stories became fodder for their parents' films. (Nora Ephron's life was particularly central to her father's memoir, "We Thought We Could Do Anything.") It was the humor that got them through, they say.
"We had actually a very difficult childhood," Delia Ephron says. "I can remember us joking about it when we were very young and getting through by just finding a way to make it funny."
"I don't think you can get through almost anything without humor," says Nora Ephron, who turned the disintegration of her marriage to Watergate reporter Carl Bernstein into the book and movie "Heartburn." "And I feel bad for the people who don't at some point understand that there's something funny in even the worst things that can happen to you."
Perhaps humor is the most appropriate remedy for sadness -- as long as you're in on the joke.