He has a serious and terrifying outie for his belly button and used it for disturbing purposes like chasing people around with his shirt up. In the game Guess Who?, he suggested them to take a picture of his belly button, but his outie was too identifiable to the other kids, so they took a picture of Tyson's arm. He also played the Name Game, and Greg was having a hard time finding a nickname that matched his personality/hobbies/looks and started with "g". He was about to choose "Great Greg", but George chose "Great George" and Greg couldn't use the same nickname as George or the teachers would think he was copying him, then Mrs. Libby suggested "Jolly Greg", but Greg isn't jolly and more importantly "jolly" doesn't start with a "g" and sadly for Greg, he couldn't come up with a "g" word fast enough, and was stuck with "Jolly Greg" the whole night.
- Diary of a Wimpy Kid: The Ugly Truth (First and only appearance)