ATLANTA (AP) _ Former President Jimmy Carter got high marks from his producer and other cast members when he became an actor for a day, co-starring with Bill Cosby in a television special for children.

In the program, ''Kids Just Wanna Have Fun,'' Carter plays himself, granting an interview to a group of middle school students. He stresses the importance of being able to separate ''a thrill from a risk.''

The Georgia Public Television production addresses the dangers of alcohol, tobacco and not wearing seat belts. Cosby plays a T-shirt vendor in the one- hour special.

Cynthia Stevens, co-producer of the program, said Thursday Carter, in his first dramatic role, ''responds well to direction. He's a very responsive actor.''

One of the students, John Champion, 13, said Carter was ''real good to work with.'' But, he added, ''He's about as nervous as we are.''

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NEW YORK (AP) - Dustin Hoffman, who has worked behind the camera as well as in front of it, said a good director knows how to ''become part of the scenery.''

The star of ''Tootsie'' and other films said he suspects he has a reputation for being difficult to work with because ''nobody really wants to collaborate.''

''It's like being in front of a canvas and some guy next to you is saying, 'No, use only this color and don't mix it with that,''' Hoffman said in an interview in the September issue of Vanity Fair. ''Each person really believes he's right, and, as a matter of fact, they both are.''

Hoffman, who has completed a film version of his revival of ''Death of a Salesman,'' said, ''The directors that I like best are the kind that don't march up and down in front of the camera before the take, but the kind that get lost, you know, become part of the scenery. And yet they're very strongly there because they know where to put the camera.''

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NEW YORK (AP) - Comedian Jerry Lewis, gearing up for his annual Labor Day telethon for the Muscular Dystrophy Association, says, ''I can't for the life of me recall how many times I've turned tears into adrenaline.''

The deaths of children afflicted with the disease constantly spur him to give more time and effort to battling it, Lewis wrote in an article for Sunday's Parade magazine.

He said his work with the MDA has given him rewards he ''never dreamed of,'' although he says contact with the children he calls ''my kids'' can cause pain as well as happiness.

''The child laughs and my heart soars ... the parents smile and I'm back in kindergarten. The nurses appear hopeful and I want to dance ... until the black veil of doom drops in and takes the child from us ... and I die again.''

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LOS ANGELES (AP) - Bryant Gumbel, morning television anchor of the ''Today Show,'' will host NBC's new monthly after-school program aimed at teen-agers, the network said.

Gumbel, who will still perform his early morning anchor chores on ''Today,'' will be host on eight ''Main Street'' programs beginning Sept. 24. ''All of the story subjects will be about young people as seen through their eyes,'' NBC said of the news magazine format.

Gumbel was chosen ''because he's extremely good with kids,'' said executive producer Herb Dudnick. ''He's done a number of pieces over the last six months where kids have been involved.''

The one-hour programs, to be produced by NBC News, are the network's entry into the after-school program market dominated by ABC and CBS. Both the ''ABC Afterschool Specials'' and ''CBS Schoolbreak Specials'' are primarily dramas.

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KATMANDU, Nepal (AP) - Nepal's King Birendra, accompanied by Queen Aiswarya, left this morning by special aircraft for Australia on his first state visit to a country in the southern hemishphere.

Before leaving, the king told his subjects that Australia has been making important contributions to the cause of international peace and justice.

''We hope the present visit will further promote the goodwill and understanding so happily subsisting between our two countries,'' he said.