A/N: Depending on how you read it, this can range anywhere from K to M. I'll leave it to you to decide for yourself what their argument was about/how it went.
Ban Hammer V
When Katara started nagging him about how he wasn't eating enough, he banned her from his office. She was furious, and refused to speak to him for a week. Even when he started joining them for dinner again, she kept her nose in the air and her back to him.
Then she decided she should convince him that there's a very good reason she shouldn't be banned. She barged in, slammed the door, and promptly sat on Zuko's desk, ignoring his angry protest.
Their argument lasted ten minutes, and reluctantly, he unbanned her. She's the only one with that honor.