Eight years ago a starry-eyed young actress plodded across a Broadway stage, said humorously inane things in a squeaky voice and sent first night audiences into hysterics. Overnight Judy Holliday's Billie Dawn became the champion of America's dumb blonde segment. Even with an Oscar on her dresser and Born Yesterday entrenched in Broadway's list of Long Runs, Judy Holliday's brand of witlessness is still unalloyed in her new movie, It Should Happen to You.

Doubtless Garson Kanin, who wrote Born Yesterday as well as the screenplay for this film, is well satisfied with his heroine's limitations. The blonde in this story is a former New York girdle model who put three-quarters of an inch onto her hipline and grew out of every available designer's pattern. Reluctant to return to Mother without achieving fame, she spends her savings to display her name, Gladys, Glover, on a four-story billboard in Columbus Circle. The ensuring difficulties confuse the other protagonists of the film while Gladys Glover remains blissfully unshaken. This unawareness, along with Glady's bewildered glances and unrestrained smiles make the humor of the film ample though Mr. Kanin's plot is thin.

Miss Holliday and her two marquee running mates attempt to make up for what the plot lacks in coherence and pace. Playing a playboy with a turn for ear kissing, Peter Lawford is his usual suave self. Jack Lemmon breaks into celluloid as Gladys' camera happy boyfriend. The latter, star of the 1946 Pudding show, seems to have picked up a new habit of dress since leaving Harvard, but his acting ability is only hampered by some of the script's insipidly sentimental lines.

In all It Should Happen to You is pleasant entertainment though there are some dull stretches. Garson Kanin has proven that given Judy Holliday he can create a funny role. And Miss Holliday, with her vacant stare, indicates that gentlemen prefer blondes because some of them are pretty hilarious.