Smell a rat 觉得可疑
I smelt a rat when he started being so helpful!
The rat race 激烈的竞争
Living in a big city is one big rat race
Play cat and mouse with sb. 欲擒故纵，（像毛抓耗子似地）欺负（折磨、虐待）某人
The policeman decided to play cat and mouse when he saw the woman steal the dress in the store.
A bull in a china shop 经常闯祸的人，笨手笨脚的人
He is like a bull in a china shop, always knocking things over.
Take the bull by the horns 不畏艰险
You can not just sit back in a situation like this. You should take the bull by the horns.
Like a red rag to a bull 使愤怒
Any staement against the government is like a red rag to a bull to that minister.
Till the cows come home 永远地，无限期地
If you are waiting for him to pay you, you will wait till the cows come home!
Paper tiger 貌似强大而实质虚弱的敌人，纸老虎
As long as we are not afraid of this kind of threat, the paper tiger’s true face will come out.
Hunt with the hounds and run with the hare 同时支持相对立的两派，脚踩两只船
Which team are you going to support? Make up your mind now. You can not hunt with the hounds and run with the hare.
Sow （the）dragon’s teeth 挑起纠纷或引起争端
Wherever he went, he sowed (the) dragon’s teeth by preaching racial segregation.
A snake in the grass潜伏的危险敌人，阴险而伪善的朋友
How could I ever trust that snake in the grass?