you could have fooled me!

informal

used to tell someone that you do not believe what they have just said

用来告诉别人你不相信他们刚刚说的话，我才不相信你呢!

"Really, I'm very happy." "You could have fooled me."

“真的，我很快乐。”“说得像真的一样。”

‘Sam never meant to upset you.’ ‘Well, you could have fooled me!’

山姆绝不是有意要让你难过。说的跟真的似的