Carl peed himself from pressure. You laughed at him, not knowing that your peeing yourself. "Well, well, well, I successfully defeated you in this challenge. I mean I laughed at you so hard, that I peed my diaper. But now is your punishment, but first I'm gonna change myself."
You changed yourself and sat on your couch, thinking, "What do I make him wear? Like, I don't want to be rude to a friend of my, but at the other hand he did made the challenge, and he would had been rude about it. I just don't know?"
As of 10 minute later, you went and told Carl things, when you realize an aweful scent was coming from the room, and saw a brown bulga in Carl's diaper. "Really, Carl. You decided to poop yourself? What a big baby! But now is your punishment, I decided that you will wear..."