As fit as a butchers dog

In the dog house

it's a dogs life

Cat on a hot tin roof   Means you are acting very jumpy or jittery

To let the cat out of the bag     to reveal something, often a secret

Cat got your tongue?   meaning  you are being very silent or maybe lost for words.   

Let sleeping dogs lie    Meaning  Leave things alone, especially is they can cause trouble

A doggie bag    A restaurant container for leftovers. 

Gone to the dogs.. the quality has significantly decreased  

like a dog with two tails 

means extremely happy