“put the cat among the pigeons”不是指“把猫放在鸽子群中”，而是（言行）造成轩然大波；招惹是非；引起麻烦。

【例句】
The principal put the cat among the pigeons when he informed the students that the excursion was cancelled.
当校长通知学生们远足取消了，这样的决定在学生中造成轩然大波。

If you tell them this shocking news, I believe that will put the cat among the pigeons.
如果你告诉他们这则可怕的新闻，我相信那将会闹得鸡飞狗跳。