If you lie down with dogs, you get up with fleas.

In the doghouse.

No one ever kicks a dead dog.

Sick as a dog.

Two dogs fight for a bone and a third runs away with it.

A barking dog never bites.

You can’t teach an old dog new tricks.

Die like a dog.

A dog in a kennel barks at his fleas; a dog hunting does not notice them.

It’s a dog eat dog world.