Like a dog with two tails - to be extremely happy
A little bird told you - someone told you a secret
A leopard can’t change his/her spots - people can’t change themselves.
To be no spring chicken - to be relatively old
Copycat - to do the same thing as someone else
The cat has got his/her tongue - to be too nervous to speak
To be fishy - to be strange/wrong; possibly criminally wrong
To have butterflies - to feel nervous
Donkey’s years - a very long time
To eat a horse - to be able to eat a lot
To get someone’s goat - to really irritate him/her
To look a gift horse in the mouth - to not be grateful for something
To talk the hind leg off a donkey - to talk a lot for a long time
To drink like a fish - to drink a lot
To be in the doghouse - to be in trouble with someone/ for someone to be angry with you
To horse around - to play around/joke
To be as quiet as mice - to be silent
To make a mountain out of a molehill - to exaggerate a problem
Not enough room to swing a cat - a place is very small
To grin like a Cheshire cat - to have a very big smile.