All Joking Aside . . .

“You’re not going to make this story all about Miss Piggy and Yoda, are you?” Frank Oz asks. “Because I don’t want anyone getting the idea that this movie is something for kids. . . .”

Certainly not. This movie--”The Score,” which opens Friday--is a high-concept, high-tech caper film starring Robert De Niro, Edward Norton, Angela Bassett and a pudgy kid with promise named Marlon Brando. Stuff blows up. And the darker side of humanity is on at least partial display. That “The Score” marks Oz’s first move into directing drama--and away from films that have made him one of Hollywood’s more consistently successful directors of comedy--should be making him a lot more nervous than his history as the voices of the aphoristic Jedi master and the celebrated ham of the Muppets.

But Oz had nothing to prove.

“For me, it wasn’t a radical shift,” says the 56-year-old director of “Bowfinger,” “In and Out,” “What About Bob?” and “Dirty Rotten Scoundrels,” who joined Muppet master Jim Henson in 1963 and made his feature directing debut with “The Dark Crystal” in 1983. “I never saw myself as a comedy director. I just saw myself as a director. And I’ve always wanted to go from comedy to action to deep, dark psychological drama to thriller to comedy.

“But what happens, as you’re well aware, is that if you’re successful at one thing, you’re offered the best of that one thing. . . .

“If I want to direct a drama--and I’ve always wanted to be a theater director, not a movie director--the dramatic scripts I’m offered are not as good as the comedy scripts. And I’ll go with the better scripts every time.”

Oz, who was born Oznowicz, and legally still is (“It’s on my checks”), had been looking for something different, “something malleable, something I could walk the razor’s edge with my actors.”

Gary Foster, who produced “The Score” with Lee Rich, concedes that Frank Oz wasn’t his first choice. “I’ll tell you the honest truth,” Foster says, “which I think is a good story. Before Frank was involved, we were developing the material and Michael Douglas became interested. So I had a meeting with Michael, and he said, ‘Have you thought of any directors?’ and I said sure, I had my list. . . . And he said, ‘Yeah, those are all good people. But I have an idea.’ I said, ‘What?’ He said, ‘Frank Oz.’ I said, ‘Really?’ ”

Really. Foster was more than a little surprised. “I said, ‘I love his movies, but they’re all in the comedy genre.’ Michael leaned over and said, ‘Let me tell you something: If I scream at you ‘---- you!’ and you scream back at me ‘---- you!,’ that’s drama. Now try to make me laugh.”

So they showed Oz the script. He liked it. They liked him. And even though Douglas dropped out, Foster says, “When it came down to it, we believed in Frank.”

Tall, gray, bearded and bald, Oz radiates a gentleness that belies his stature. And a certain humility. “My attitude was, as I told my DP [director of photography], Rob Hahn, ‘Let’s take a big chance. Huge chance. That way, the worst that could happen is they’ll say, “Frank Oz can’t direct anything but comedy.” And we can go back to comedy.’ That’s a great freedom.”

With a story by Daniel E. Taylor and Kario Salem and a screenplay by Salem, Lem Dobbs and Scott Marshall Smith, “The Score” stars De Niro as Nick Wells, a highly proficient and strictly discreet safecracker whose cover is a Montreal jazz club and whose girlfriend (Bassett) would like him to retire.

Having never been caught and wanting to keep it that way, Nick is ready to call it a career when his fence, Max Baron--played by a scene-heisting Brando--cajoles him into one more caper: the theft, from the almost impenetrable Montreal Customs House, of a priceless French scepter. What makes the job irresistible to Nick and sets his warning lights flashing is Baron’s inside man--a cocky Nick-in-training named Jackie Teller (Norton), whose cover, as a mentally impaired maintenance worker, has provided him access to the security system.

“I love ‘Topkapi,’ ” Oz says of the classic 1964 Jules Dassin heist film. “But I’m not a big caper fan. And I didn’t set out to make a caper/genre film. To me, it’s character driven. I always intended it to be a character film--although we had a really cool caper. But what appeals to me is the push and pull the characters have against each other. . . . I don’t think in genre form ‘cause that means I’m slotted into doing things in a genre form. . . . I just have to go on the honest impulse.”

Honest impulse. Despite all the laughs he’s gotten throughout his career--including directing pal Steve Martin in “Housesitter” and “The Little Shop of Horrors,” or via his cameo appearances in “The Blues Brothers” and “Trading Places”--Oz says he doesn’t “profess to know comedy, or drama,” he says. “I hope I never know comedy or drama, because as far as I’m concerned, as soon as you ‘know’ something, there’s nothing left to discover.”

On his deathbed, a famous actor reportedly said, “Dying is easy; comedy is hard.”

Oz would concur. “Comedy is riskier. If you don’t make the audience laugh every 10, 15 minutes, it ain’t a comedy. [In] drama, there’s fewer risks. In comedy, every time you attempt a laugh and don’t get it, you’ve [messed] up. In a drama . . . it’s not easier, exactly, but the risks are smaller.”

Of course, as Oz has said, he never wanted to become a film director. He never wanted to become a puppeteer. And during his maiden voyage to the United States--he was 5, traveling with his family by ship from postwar Europe during a hurricane as “tables were flying through the air”--he probably had doubts about coming to America.

And yet, it appears to have worked out. In the Oz apartment on Manhattan’s Riverside Drive, which he seems to keep as a memento of less glamorous days in New York (as a college student, would-be journalist and Henson collaborator), there are cases with puppets and puppet heads that Oz’s carpenter grandfather carved some 60-odd years ago, including a ragged Adolf Hitler that the family buried in occupied Holland, and then dug up after the war.

“I’m very proud of them,” he says of his Flemish mother and Dutch father, who uprooted the family to England while fighting Nazis with the Dutch Brigades, “because most immigrants come to the United States and join other immigrants to be secure. And they made a point of not doing that.”

Eventually, the family settled in Oakland, where young Frank originally “did” puppets to please his parents--pleasing, much later, a lot of other, shorter people as a member of Henson’s original Muppet troupe and the voice of Miss Piggy, Fozzie Bear, Grover and other furry creatures.

You can’t resist asking: Who’s tougher? Miss Piggy or Brando?

“He’s a very sweet, gracious, childlike in some ways, very, very humane, very complex person,” Oz says of Brando, taking unspoken note of the reported tension on the movie’s Montreal set. “But I can’t say that we got along all the time. And it wasn’t because he was difficult; it was a difficult situation. I don’t want to do a puffery piece here, I want to be flat-out true: We had a difference in creative interpretation of the role. He felt one way, quite sincerely and earnestly, and I felt the other, and the producers backed me which I’m grateful for, and Marlon did come around to my side.

“But that caused a rift between us,” says Oz, and partly because of that, “I wasn’t able to direct, or you know, discover things with Marlon. But it wasn’t because he was difficult. He’s an easy target. I think it was as much my fault as his fault.”

For De Niro, Oz has nothing but grateful praise--not just for his work, but his connections: Mick Gould, for instance, who served as technical advisor on the heist. “He showed us how to crack safes,” says Oz. “Everything is real in the movie; nothing is phony. Every piece of equipment was passed through Mick.”

And De Niro? “There’s no one as an actor--no one, I think, as a human being, too--but no one as an actor that I know of who’s as honest in his impulses as Bob.”

After De Niro, no one gets more effusive praise from Oz than the late Jim Henson--who, virtually by accident, saw Oz perform at a puppet fair when he was 17, and later asked him to join the troupe. They did commercials and TV specials with Bob Hope, Perry Como and Dinah Shore before moving into “Sesame Street” and then “The Muppet Show.” Oz still does work for “Sesame Street”--”maybe two times a year.”

“At home [in Connecticut], I just want to be a dad. I don’t want my children to be the son of someone. Once in a while one of their friends might say, ‘Don’t you do the voice of . . .’ and I say, ‘No, I’m just a dad . . .’ ” Of course, he’s a dad who makes major motion pictures, and takes the work seriously. “There are no big explosions and killings in ‘The Score,’ ” he says. ‘Not that I’m against explosions. Or killings--Shakespeare has a fair amount of killings, as I recall, and the guy’s no slouch as a writer. I look forward to movies where I do killings. It’s great. Sex. Everything. I look forward to it.”

Then he tempers his enthusiasm with what might serve as his motto.

“But let’s motivate it properly.”