Stephen Chow plays a rich playboy who is blown up by a mafia boss when he flirts with the boss's girl. Through a series of circumstances his professor makes him a synthetic (robotic) body that allows him to change into a variety of "Mrs. Wong's Household products" like a microwave and toothpaste. Chow eventually goes to work at a school notorious for it's rowdy students and singlehandledly disciplines them all. He then goes on to marry a former classmate played by Gigi Leung. But before the wedding happens, the mafia boss finds out that Chow is still alive and sends in his own human-robot to take Chow out for once and for all. 星光。以不变应万变。百变星君——童年挚爱。经久不衰的星爷幽默。不是抨击现实，而是远离现实。回顾星爷的作品（38）。不变的情。无厘头未必高明。喜欢星爷的理由之《百变星君》。无聊的生活不值得赘述。 夏威夷念大学的香港富豪子弟李泽星（周星驰 饰）学业无成挥金如土，是校园一霸，终因搭上黑帮老大情妇遭黑帮追杀，身体被炸成碎片。 在李泽星父亲（吴孟达 饰）的请求下，教授（徐锦江 饰）将李泽星全身人造复原，并把最新研制成功的无敌芯片置入其身，令其摇身一变成为无敌“百变金刚”。黑帮老大得知李泽星复活后，将写有战争程序的芯片植入手下身体，令其变身“铁甲威龙”前来追杀李泽星。为赢得暗恋的女同学虫虫（梁咏琪 饰）的芳心，李泽星决意重塑形象，奋力与“铁甲威龙”展开大战。
