Before their Saturday evening performance the quartet of lovely young ladies in "Brother Rat" at the Plymouth Theatre all agreed that the audience laughed long and hard at John Monk's and Fred Finklehoffe's first comedy.

But as pretty Marie Brown, who plays the bespectacled colonel's daughter, put it, "the audience can't get half the kick out of it that we do. Still, Boston people are wonderfully receptive to comedies and musicals."

Dark-haired Miss Murphy, the understudy, when questioned about the authors, raved: "Oh, they're the most wonderful guys you ever met. They both graduated from V.M.I. Finklehoffe became a lawyer and Monk an actor; now they're collaborating on another play."

Wrapping her kimono around her pink slip, Florence Sunderstrom, the blonde heroine, crossed her Dietrich-like legs and answered a question, "No, I don't mind Eddie's 'surprise attack'; it's a lot of fun." Billy Randolph, played by Eddie Philips, uses army tactics in making love to Florence.

Then Mary Cheffey, in the play the secret bride of a V.M.I. first-classman, burst in the room: "What is this, an interview? How cute!" She smiled at a delicate question and said: "I'm used to being pregnant eight time a week, but I get embarrassed when the audience laughs!"

When the play finishes, which they all hope will not be for some time, the girls plan to return to New York to look for a new job. Miss Brown voiced their feelings as she applied the last daubs of make-up and scampered out: "Hope this will be a lead to something else."