Smell a Rat
注：feel that something is wrong
Frankly, I smell a rat.
Go to the Dogs
Have you seen their house lately? It's really gone to the dogs.
注：strange and suspicious
A: Something's fishy.
B: I'll just go check it out.
Take the Bull by the Horns
注：take decisive action in a difficult situation
She had been putting off taking lessons, but she finally took the bull by the horns and went to a professional dance studio for help.
Horse of a Different Color
注：quite a different matter
A prank that hurts someone is a horse of a different color!
Let the Cat Out of the Bag
He wasn't supposed to know about it, but someone let the cat out of the bag.
For the Birds
注：uninteresting and meaningless
As far as they were concerned, it was for the birds!
Straight From the Horse's Mouth
注：from a reliable source
I got the information straight from the horse's mouth!
Cat Got Your Tongue?
What's the matter? Cat got your tongue?
Don't horse around in here or you will break something.