Look what the cat's dragged in spoken language informal
This phrase is used to greet someone when they arrive in an insulting and playful way and show your disapproval of them.
Everybody, look what the cat's dragged in! Mike has just come back from the honeymoon. How was it, Mike?
Peter once said he would never be in the same room with me, but now look what the cat's dragged in!
Look what the cat's dragged in! He said he won't come here again.
Someone who is foolish and annoying; an idiot
To say bad things about someone to damage their reputation
The origin of this expression is not clear. However, it is supposed to be derived from the early 1900s, related to domestic cats' habits of bringing the parts of animals that they hunted back home.