Everybody who grew up with him was there - Jimmy Carter, age 54; Rosalynn Carter, age 51, and Amy Carter, age 11.

It was his 50th birthday party and he didn't look a day older than when he first peeked out of the mousehole on Walt Disney's drawing board in 1928. The public got its first look on Nov. 18 of that year when he starred in a short sound cartoon titled "Steamboat Willie" at New York's Colony Theater. The next day it was in all the papers that a star had been born and the mouse that started out merely squeaking and whining eventually roared its way into movie houses - and hearts - around the world.

Yesterday, in the East Room of the White House Mickey Mouse took his bows as they serenaded him with "Happy Birthday," making it surely one of the more memorable White House birthday parties.

"You know," said an artist who used to draw Mickey back in his Hollywood heyday and who had accompanied him on his 18-state, 57-city whistle stop tour from California, "this mouse could run for president."

Not that anybody would have doubted it. From the moment the Disney World Combo struck up the Mouseketeer National Anthem and Mickey, with his arm linked through Amy's, walked into the East Room, he was nobbed.

There was a gold-and-white birthday cake covered with a picture of him in colored frosting, and there were hats for everybody - the kind with ears, of course. The guests were more than 100 developmentally disabled and mobility-impaired youngsters from the D.C. public school system.

On stage, Mickey was happily hugging Amy or showing her a cavalcade of dance steps he had perfected through his half-century in show biz. She caught on pretty quickly considering the generation gap and the audience was ecstatic, sometimes even joining them.

When the president arrived, he got up there with Mickey and Amy, too, and motioned mom to join them. The moment was too good to let slip by without a memento so ard Kimball, the Disney artist, did a quick cartoon of Mickey, signed it "Hi, Jimmy" and slipped it to the president.

In Kansas "people were waiting in the snow at 1 o'clock in the morning so their kids could see Mickey when the train stopped at the depot," Kimball said of the tour, convinced that Mickey will bo "on a coin someday."

Splendid in red pants, black cutaway coat, yellow bow tie and white gloves, the big-eared, bulbous-footed mouse had started out as a gleam in Walt Disneys' eye on another crosscountry train ride.

"I had this mouse in the back of my head . . . because a mouse is sort of a sympathetic charactic in spite of the fact that everybody's frightened of a mouse . . . including myself," Disney said later.

The red velvet pants were there from the beginning, but not the name. Disney called him "Mortimer" but Lilian Disney, his wife, thought it too pompous and campaigned, instead, for "Mickey."

By the time Franklin Roosevelt moved to the White House, Mickey had become a national hero and a White House regular - on screen. Eleanor Roosevelt once wrote Disney to tell him that Mickey was one of the president's favorite movie stars.

Other presidents too, were Mickey Mouse fans and all except Lyndon Johnson, according to Disney people, personally met him on stopovers at Disneyland and Disney orld.

The only dark moment of Mickey's otherwise triumphant national tour this week apparently came when a wire service reporter wrote that a woman, not a man, was portraying the good mouse. Yesterday Arlene Ludwig, a Disney publicist, refused to comment other than to insist "it's a mouse, it's a mouse, it's a mouse."

Not that it really mattered.

When the party was over and Amy Carter was saying goodbye, Mickey Mouse pulled up his coattail and wiped away a tear. Of mouse and man or of mouse and woman, a tear is a tear is a tear.