Bill and Bette Fisher sat on the set of "Good Morning America" in the ABC news headquarters in New York last night watching their most recent houseguest, the president of the United States, tell the American public: "I realize more than ever I need your help. . . . I left Camp David to listen to other voices - men and women like you." And when Jimmy Carter was finished, Bill and Bette Fisher decided that it was good, that it was very good.

"I liked it," Bette Fisher said.

"I wasn't sure before he gave his speech, but now I think he has a good grasp on what's going on. I think he's given people real direction," Bill Fisher said.

Then, with millions of Americans watching, the Fishers went live on national television - just plain folks, the other voices the president talked about - and said they even heard a little bit of what they told the man just four days before on their back porch in Carnegie, Pa.

"We talked about mass transportation," Bill said. "And I remember talking about how we sensed this depression in the country, how we weren't at all optimistic about our future."

Throughout the speech they listened attentively. Bette in a very short skirt. Bill in an open collar. He was especially transfixed during the speech, his left leg crossed over his right, his right hand balanced on his left boot. It was almost as if the uncommonly forceful tone the president used had riveted the 29-year-old machinist to his seat.

"I think the country knows now," Bill said, "that it has a president who listens."

Once even, the president spoke directly to Bette Fisher, saying: "This from a young woman in Pa. - 'I feel so far from the government.'"

"I said that," she said.

And she smiled.

It's in the books now. They'll never take it away from her.

"If this is a dream, don't wake me up. Let me keep dreaming." - Bill Fisher

Bill Fisher remembers exactly what he did on Thursday night when he found out that the president - that big man himself - was coming over to chat. He turned to his wife, Bette, his palms extended and with his eyes, said: "Give me five."

Which she did.

And from that moment on, life for the Fishers, a couple of just plain folks from Carnegie, Pa., has been a nonstop-all-systems-go-two-tickets-to-Paradise-far-out-far-freakin'-out trip.

Thursday it was the Carters. Friday and Satruday it was the media blitz. Yesterday it was a flight to New York for an appearance on ABC News to comment - Can you believe it, to comment? - on President Carter's nationally televised speech. Today it will be the "Today" show on NBC. Tuesday? Who knows? Maybe by Tuesday, they'll be so popular they'll host the "Tonight" show.

"It's crazy," Bill said as the cab pulled out of LaGuardia airport yesterday afternoon.

"Yeah, it's crazy," Bette said. "But we love it."

"I mean you can't believe the reaction," Bill said, "People'll drive by the house and slow down and wave."

"Isn't that neat?" Bette asked.

"I got this friend, who is vacationing down in Virginia Beach, you know," Bill said. "And he saw us on TV after the president left. So he calls me and says: 'Hey Fish, I saw you on TV, man. I'm down here in Virginia Beach, and I turn on the tube, and what do you know - there's Fish on TV.'

"But that wasn't the funniest thing. The funniest thing was that my Dad was watching the Pirates game on TV on Thursday, and in the seventh inning they broke in to say that President Carter was on Charles St. in Carnegie, so my Dad jokingly says to my Mom: 'He probably stopped in to say hi to Bill and Bette.'

"So after the president left, I called my Mom and said: 'You'll never believe who was just over here to dinner - Jimmy and Rosalyn Carter.'

"So she says: 'Yeah, what else is new.'

"She thought I was kidding."

Does it sound genuine? Does it sound like a couple of kids having the time of their lives? Well, it should. Bill and Bette Fisher from 723 Charles St. in Carnegie, Pa., are smart enough to know you only go around once. Grab for the gusto? These two are reaching out with an industrial strength magnet.

He is 29, but he looks younger. He's a graduate from the Citadel with a degree in political science, but he works as a machinist because he likes working with his hands. She is 25, with a pair of eyes that are so brightly blue they ought to be painted on the hood of a fastback Camaro. They have a 13-month-old daughter named Alison and a two-story house. They didn't even vote in the 1976 presidential election.

"I don't know why they picked us to visit," Bette said. "All I know is a friend of a friend of a friend knows somebody in Washington."

Yes, they qualify as little people, real people, the kind the Jimmy Carters of the world need to hear from and maybe ought to listen to.

"I just love the way he calls her 'Bett-ah," Bill said.

"So nice to see you, Bett-ah," Bette said.

They knew someone from the White House was coming, but they had no idea it would be him until Pat Cadell, the presidential pollster, told them so 50 minutes before the Carters showed up.

"My heart started beating real fast and I got that weak feeling inside," Bette said. "When I met him, gee, my blood was really flowing. But when we were all sitting there it was just like talking to Uncle Jimmy and Aunt Rose. They were so relaxed. I gave him some lemonade in a styrofoam cup. He drank it all, so he must have liked it."

"Yeah," Bill said. "I mean it was so relaxed. I wanted to say: 'Hey Aunt Rose, what's up?"

"Sometimes," Bette said, as the cab pulled up to the hotel where NBC had reserved a room for them last night, "Sometimes it feels like it didn't even happen."

Two hundred and fifty million Americans have seen it or read about it or heard about it. It happened all right. If the world is truly composed of an infinite number of people who get 20 minutes of celebrity, the Fishers want the full 20.

"I had this crazy feeling that the wall was going to fall on the president," Bill said. "Our wall next to the steps that lead up to the house is all cracked and broken. I swear I thought it was going to fall on him."

Of course it didn't. And he didn't get ptomaine from the lemonade. And he didn't slip and fall in the bathroom either. And when it was over, he left them an autographed pen.

"I was hoping for a gold peanut," Bill said.

And now they are in New York about to be asked to comment on a speech, like their last names were Sevareid or something.

"I guess they'll just ask us if what he said to us was what he says to the American people, just to see if they coincide," Bill said. "Some people have asked us if we feel exploited. I don't. There's always that chance, but deep down I don't feel that way. I think from now on, we'll probably watch the government a little more. A lot of people have told us they think of us as their spokesman."

As the Pumpkin Hour drew close, the Fishers thought about what's next for them, what happens when they go back to Carnegie, him to his machinist's job, her to her baby. What happens to footnotes to history after the page is set in type?

"When he left we thought it was all over," Bill said. "They said we might be contacted by the press, but we never imagined it'd be like this. We turned the lights off and closed the door, but it didn't stop. When we finally had to leave the house to get away, the phone was still ringing."

"We didn't get much time to ourselves," Bette said.

"When we did, we watched ourselves on TV, and we'd be jumping up and down screaming," Bill said. "We were like a couple of high-school kids. We really let it out."

His eyes flashed when he spoke, like he and he alone had Jaclyn Smith's unlisted phone number. Had it been night, you wouldn't have needed a flashbulb to take his picture.

"But you gotta try to be cool about it," he said."I mean you can't start getting a swelled head about it, you've gotta watch your hat size."

"The thing is," she said, "after this we have to go back to just being Bill and Bette Fisher again. We were just lucky - that's all." CAPTION: Picture, Bill and Bette Fisher in New York yesterday; by AP; Illustration, no caption, By Alice Kresse - The Washington Post