Stealing Warren Beatty's wife onscreen should not be a laughing matter, but in Heaven Can Wait Charles Grodin proves himself, if not the most brazen adulterer in the history of movies, certainly one of the funniest. His furtive bedroom romps with Dyan Cannon have helped raise Heaven's grosses to the skies ($50 million and still counting). But even Dyan's professional reputation as a Hollywood heavyweight cannot rival that of Grodin's earlier co-star; in King Kong he played the villain who exhibits the great ape before being squashed with one simian stomp. (Grodin's well-deserved if gruesome demise was shown in Kong's two-part TV premiere on NBC last week.)

Grodin portrays such "funny jerks" (as he describes the roles) with a believability that is making the 43-year-old actor one of the most successful in the business. Yet it's hardly changing an oddly anonymous life that has all the star quality of a black hole. "I used to have a hot plate," deadpans Grodin. "Now I have two hot plates." His pal Paul Simon calls Grodin's unflamboyant life-style "the clearest manifestation of a neurosis." A young woman Grodin recently drove home from a party took one look at his 10-year-old Dodge and laughed. His humor is just as economical. "It's hard to tell when he's being serious and when he's being funny," says Beatty. "That's a hallmark in people with great comedic gifts."

Grodin figures, "I'm not competitive, ambitious or jealous." Indeed, he was the first choice to play The Graduate but lost out to an unknown Dustin Hoffman after balking at the contract. Later Grodin yawned at playing an ichthyologist in the project that became Jaws. (Enter Richard Dreyfuss.) Conversely, Grodin took the Kong role after George C. Scott, Robert Mitchum, Peter Sellers and Peter Falk vetoed it. When Falk wired, "How will you play the part?" Grodin replied, "With a toga and an earring." Falk later said admiringly, "That son of a bitch always finds a way to do it."

Grodin grew up in Pittsburgh, where his late father, Theodore, sold cleaning supplies. At Peabody High School young Charles was valedictorian and a sports buff, but never ventured onstage. Then, inspired by Montgomery Clift in A Place in the Sun, he decided "acting looked easy and Clift looked natural. It turned out it wasn't easy and acting natural wasn't what he was doing." At 18, Grodin dropped out of the University of Miami and wound up in New York, a "totally withdrawn kid." He studied with Lee Strasberg and Uta Hagen while working as a cab driver, night watchman and in the post office. He broke into movies as the obstetrician in Rosemary's Baby—"My agent is probably the only other guy in the world who knows I was in it." By the time he surfaced as the newlywed cad who runs off with Cybill Shepherd in The Heartbreak Kid, he had been acting for 20 years. He has appeared in some 75 plays, including Broadway's long-running Same Time, Next Year with Ellen Burstyn. Grodin has also produced and directed on Broadway (e.g., Thieves with Mario Thomas), authored a play and this month he was up for an Emmy for writing a Paul Simon TV special. Later this fall Grodin will co-star with Carol Burnett on CBS in Erma Bombeck's The Grass Is Always Greener over the Septic Tank. Ready for release is a film inspired by PBS's Loud family, titled Real Life, in which Grodin plays a veterinarian whose life is invaded by a movie crew.

Happily single since he and his wife, Julia, were divorced a decade ago, Grodin lives in Trappist solitude in a script-cluttered sanctum on Manhattan's West Side. It is off limits except to close friends like playwright Herb Gardner and actor John (Ryan's Hope) Gabriel. One exception is his daughter, Marion, 17, a college freshman, who visits regularly. Though he's dated Louise Lasser and, lately, Teri (Close Encounters) Garr, Grodin delights in walking into a restaurant with his famous pals—and being the only one unrecognized. Such privacy may end, though, after his next project, Sunburn, a comedy thriller co-starring Farrah Fawcett-Majors. Does he have the romantic lead? "Who else?" Grodin shrugs. "The only other star in the picture is Art Carney."