"Just think," Ronald Reagan said last night from center stage at the Kennedy Center's Opera House, "if you haven't heard it yet: Bob Hope is 80. Bob, can I call you 'Pops'? I love it when you call me 'kid.' "

The president was reading from cue cards in the back of the room, as did the 20 other acts that sang, danced or joked their tributes to Bob Hope. It was a USO benefit and taping of a three-hour show, "Happy Birthday, Bob," which will air on NBC (Channel 4) at 8 p.m. Monday.

"Only in America can an ex-hoofer from Cleveland be sitting next to an ex-disc jockey from Iowa in the presidential box," Hope said.

The comedian said he was afraid to ask for room service at the White House, because "I didn't know what to tip David Stockman." He said he's stayed at the White House before and has learned not to sign anything while he's there because "last time, I accidentally vetoed three bills."

Hope said he stayed over with the Reagans on Thursday. "I know Ronnie is trying to balance the budget, but $180 a night is pretty steep."

The Ron and Bob routine never let up.

When George Burns took the stage, to a standing ovation, he said to Hope:

"Eighty, huh? How does it feel to be 80? When I was 80 I had pimples."

Phyllis Diller seemed to be the supreme show-stopper and Reagan's favorite. She appeared wearing a wide-shouldered purple and gold mini-dress, with spike-heeled gold boots. She talked about Hope being cheap.

"Once he took us out for coffee and donuts. The kids loved it. They'd never given blood before." Reagan leaned back in his chair, almost crying with laughter.

Then Lucille Ball came on the stage, also to a standing ovation. "Bob looks wonderful. And so do you, Mr. President," Lucy said. "By the way, Mr. President, do you have to give so many televised press conferences? Every time you go on, you pre-empt about 100 'I Love Lucy' reruns."

Lynda Carter and military bands were the show starters. Carter sang her version of "Hey Big Spender": "The minute you walked in the joint . . . Hey, Bob, honey/Sweet and funny/Hey, Bob, honey, spend a little time with me . . ."

At that point, Hope leaned over to Reagan and said, "I'd better check my schedule." The two laughed.

Before the jokes and taping started, and before Nancy Reagan and Dolores Hope joined their husbands in the presidential box, director James Lipton came on stage.

"This is what is called in television a 'warm up,' " Lipton told the almost-full house. He gave the audience--which included Secretary of Defense Caspar Weinberger, press secretary James Brady--instructions about what to do and, more specifically, what not to do.

He then explained that he needed to film the audience clapping before the real show began, to be edited into the final program for television. "So now let's have a big round of applause," Lipton said. "Don't stop until I ask you to stop--about three days." The crowd then gave three separate standing ovations--all for nothing.

Then on with the show. Tom Selleck offered a short monologue. Flip Wilson did his Geraldine routine, with wig, shiny purple dress and turqouise shoes.

"Ronnie, baby. I saw you at the White House photographers' dinner . You got a sense of humor, Stuff. I almost fell off Killer's lap when you did this thing." Geraldine imitated Reagan's thumbs-in-ears gesture and the crowd, including Reagan, burst into laughter.

The acts moved on and off stage quickly with Loretta Lynn, Sheena Easton, Howard Cosell, boxers Roberto Duran and Marvelous Marvin Hagler.

Ann Jillian and dancers did a number for which, according to one cameraman, the sound was taped in New York earlier. Jillian mouthed the words.

Following were: Julio Iglesias, Dudley Moore, Kermit the Frog, Barbara Mandrell, Christie Brinkley, Brooke Shields, Cheryl Tiegs, Kathryn Crosby. There also were birthday greetings, including one from Pope John Paul II, read by George C. Scott; Reagan's jests; a USO gift for Hope, and Hope's act. All that was followed by the full cast and the Reagans on stage with three birthday cakes for Hope.

"You can tell the president had a lot on his mind tonight," Hope said. "Halfway through he asked Nancy to get up and change the channel."

And it was Hope who had the last word, with his trademark: "Thanks for the Memories."