When Gertrude Lawrence sang and wiggled her way through 'Jenny' several seasons ago in "Lady in the Dark," first-balcony subscription spinsters bravely acquiesced before the onslaught of the general delight. With a play as hilarious as it is a perfect starring vehicle, it is now Helen Hayes' turn to toss her admirers a wicked bump.

"Happy Birthday" is an epigrammatic field day for novelist Anita Loos. Like Saroyan's "Time of Your Life," the setting is a saloon: the Jersey Mecca Cocktail Bar in Newark. Across the stage passes a steady procession of Everyman inebriate--the abortionist and his clients, the cop and his yeggs, the tarts, the footloose old maids, and the young businessman out on the make. Joining in the merry-making--by cautious degrees, to be sure--is Addie Bemis, librarian, who swills three "Pink Ladies" and throws repression to the winds. It's the happy Birthday of her life, the day she first drops inhibition and learns sex exists outside of Boccaccio.

Miss Hayes makes the most of her one-woman show. Torching a custom-built Rodgers-Hammerstein number, 'I Haven't Got a Worry in the World,' or toasting everyone in sight from a tectering perch atop three bar stools (sample: "May all your troubles be little ones and may all your little ones be yours"), she renders choice Loos-isms classic. Her love scene under the table with Louis Jean Heydt, staged to the exactly appropriate subdued degree, is something you are not likely to forget.

While the writing lacks direction and in the final analysis seems to have gotten nowhere, the failure in impact is amply compensated by uproarious dialogue and a certain wackiness which can only be described as "Anita Loos." Tops in froth, Miss Loos drives her sharp-edged, relevant humor home with a vengeance. Whether a theme can be detected in the midst of it all is moot. You may not know what it is all about when the shooting stops, but you'll know you liked it.