AN electrifying buzz swept through JJ's when news went around that Larry Bird, the American basketball legend, was doing a mean lambada on the dance floor. Sitting with some friends in the Music Room of the tony nightspot, Keeping Posted was accosted by excited waiters and customers proudly displaying tablemats on which the great Boston Celtic cager had inscribed his treasured scrawl. At this stage, accompanied by JJ's manager, Larry Cowle, who sent one of his staff scurrying to organise a camera, we decided to go downstairs to the disco area to press the flesh with the towering NBA star and check out what exactly he was doing in town. The first indication to Keeping Posted that something was amiss came when Cowle pointed out Bird. We found that we could actually look him in the eye without first having to stand on a chair. Then there was the little business of the waistline. Bird may have been retired for just over 12 months from the sport, but still not long enough by our estimation for him to have developed such a significant paunch. By now Keeping Posted had guessed the score, but Cowle - and, indeed, many of the customers, still needed convincing (the excuse of the JJ's manager was that he hails from San Diego, where they are only interested in baseball!). Cowle did eventually go up and introduce himself with the no holds barred line: ''I am the manager here and I understand you are Larry Bird.'' Twitching with embarrassment, Bird then came clean: ''Actually, my name is Paul. I was just having some fun.'' Word quickly went round JJ's to that effect. And before long this Bird had flown. Torn up tablemats soon littered the floor like confetti. JJ's staff, meanwhile, have been alerted to be on the look out for Elvis Presley.