You are kidding.(你在开玩笑吧。)
A:Tony,I'm thinking of cutting my long hair.What do you say?
B:You are kidding.
A:No,I'm not.I'd like to change my image for a while.
B:All right.It doesn't hurt anything if you change your hair style.
A:托尼,我正在考虑把我的长发剪掉。你觉得怎么样?
B:你在开玩笑吧。
A:不,没有。我想改变一下形象。
B:好吧。改变一下你的发型无伤大雅。