the dog days of summer
What is canicular days?
Love me, love my dog.
If you love someone, you will like all that belongs to him/her.
in the doghouse
If you are in the doghouse, someone is annoyed with you and shows their disapproval.
have butterflies in one's stomach
How did you feel before you made a speech?
rain cats and dogs
It's nice weather for ducks.
Barking dogs seldom bite.
Don't be afraid of dogs that bark or people that threaten you (say they will do something bad to you) - in both cases they rarely take action.
Every dog has its day.
Don't look down on him though he hasn't got a penny to his name. After all, every dog has its day.
in a dog-eat-dog world
The expression comes from the Latin saying "a dog does not eat another dog." It describes a situation where people will do anything to be successful.
like a fish out of water
Not knowing anything about music, I felt like a fish out of water among so many musicians.
with crocodile tears
If that the earth could teem with woman’s tears, each drop she falls would prove a crocodile.(Othello, Act IV, Scene i, Othello convinces himself that his wife is cheating on him.)
to let sleeping dogs lie
We should let sleeping dogs lie. They're both adults. Let them make their own decisions.
to go to the dogs
This used to be an excellent newspaper but in recent years it has gone to the dogs.
You can't teach an old dog new tricks.
The opposite one is "You're never too old to learn".
the elephant in the room
"Let's first acknowledge the elephant in the room."
--Zootopia
have ants in the pants
What is ANTS and PANTS?