You have a classmate named Leo and you can never remember his name. You and him got partnered for a project

He sits next to you and starts working on his side of the project. Class was over and you didn’t finish it yet. So he asked..

Leo: “Want to come to my house and finish this project? I doubt that you want to spend your whole day at school working on this project, right?”

You were going to say ‘sure, Leo’ but you can never remember his name so instead you said..’yes, sir.’ Eventually it’d turn into an inside joke.