你举的例句不对.应该是you must be kidding (me).OR you have got to be kidding me.(别开玩笑了!).kid,小孩子.作动词用,把某人当小孩子.be kidding me 直译为"把我当小孩子",转译一下,就成了“开玩笑!”“哄我玩呢!”