be a doll

informal

1. To be especially agreeable and helpful. A: "Hey Elaine, I found the files you were looking for." B: "Oh, you're a doll! Thank you!" Hey, be a doll and go get me a cup of coffee. A: "Would you be a doll and sit in this meeting for me?" B: "The boring budget meeting? No thanks."

2. To be cute or otherwise physically attractive. Typically said of small children. A: "Have you seen Pat's daughter? She's a total doll." B: "Oh, I know! And she's walking now too, so look out." Alex's new girlfriend is a doll—and a real sweetheart too. Oh my goodness, look at her in her Christmas dress! She's such a doll.