'Titanic' star Billy Zane sails onto the set of ABC's "Samantha Who?" for a guest appearance on tonight's episode opposite Christina Applegate, and we're on the set with the stars for their long-awaited reunion!

"I immediately jumped at the opportunity," Billy tells ET's Kevin Frazier. "I was a big fan of Christina's for years, and the show is hysterical, and it was a chance to spring some comedy chops while still sporting fine threads."

Billy plays Samantha's ex-boss, billionaire Winston Funk. While in Las Vegas to attend a real estate seminar, Samantha loses a huge sum of money playing craps. But could Winston be the answer to her financial woes?

"He's on a learning curve through his love of Sam and her new lease on life," Billy explains about his character. "Her new perspective is certainly schooling him. His desire is maintained, if not increased, because now she's the prize he can't have."

"There are moments that she starts to fall [for him]," says Christina. "But he's not that good of a guy and she knows that, so it's like a push-pull thing, trying to resist him as much as possible."

Billy's role marks a reunion for the two stars, who worked together on an episode of the TV show "Heart of the City" way back in 1986. "We were really young," he says. "[It's] ironic to come full circle however many years later."

"I was so young then, so I don't really remember much," says Christine with a smile. "I was 14 years old. A lot has happened since then."

And Billy doesn't hesitate to heap praise on his co-star, saying, "She's got it in spades. I think she was certainly the best comedic actress this year or any -- just incredible comic timing, grounded in real stakes. She's a true actor."

"I love Billy," responds Christina. "When he comes to work, he's always dressed really nicely and really put together. He's a very sophisticated and interesting guy."

Watch ET for more with Billy and Christina in "Samantha Who?"