you've got to be kidding me.
是have got to的缩写,是一定的意思,表示肯定的推测.
be kidding me就是正在开我心,开我玩笑,是现在进行时态（说话时正在进行的）.
这句话就相当于you must be kidding me.
have got to就等于must,是must的口语说法.