To look like something the cat's dragged in is to be dishevelled or very untidy. - Wiktionary.

Am rough around the edges and she did not have to announce it. I was bent over and working, a white woman walked in followed by a white male. The woman said, "Look what the cat dragged in." They passed me and I looked to see if there was a cat. No cat, no rat, no mouse, no house.