ANYONE wandering into the lobby of the Hong Kong Convention and Exhibition Centre last night might have thought the entire place had suddenly gone daft. Giggling girls were getting their arms autographed by a man with a megaphone claiming to be Steven Spielberg. Nearby, another man conducted an imaginary auction, while another walked an invisible dog and a short Scottish girl played a cheerleader named Candy, waving pom-poms and chattering in an American accent. These were not pranks at a party, but part of the lavish entertainment provided by hypnotist Paul McKenna. A sell-out crowd greeted the one-night appearance of the man made famous by the British television series, The Hypnotic World Of Paul McKenna. Wearing a red jacket over white tuxedo shirt, he wasted no time in putting dozens of volunteers into a trance. McKenna took them to the races - without horses. He turned them into goldfish. In one hilarious bit, he had them pulling the shoes of the person next to them, convinced these were really mobile phones. Hypnotism can elicit alarming honesty. The victims were told to imagine themselves at work on a typical Monday. The result was the predictable pounding of computer keys for most, but one fellow didn't respond. When McKenna could not snap him from his slumber, he asked: ''What are you doing?'' ''Sleeping,'' came the reply. ''What's your job, then?'' ''I pretend to be a property consultant.'' The show kept up the pace even during the intermission with the bizarre cast of characters doing their spontaneous, wonderfully unpredictable and utterly convincing stuff.