A STRANGE tale reached our desk last week about American singer Bobby Brown and his predilection for Hongkong's nightlife during his recent visit. Not for Brown the trendy lanes of Lan Kwai Fong - the normal outpost for in-town performers. Instead, he and his entourage of beefy bodyguards made their way down to Wan Chai nightspots Neptune and the Big Apple several times during his time here. As we heard it, during the course of one evening Brown found himself locked inside a cubicle in the ladies' toilet at Neptune, having entered it with a mystery female companion. When members of Neptune's management started hammering on the door, Brown hissed at her twice to shout the word ''dog''. She ignored him once, then yelled ''dog'' with all the power in her lungs . . . only to discover it was the code word for the singer's minders to rush in without delay and return him safely to the dance floor.