Greg Heffley is the main antagonist in The Diary of a Wimpy Kid series and films. He is portrayed by Zachary Gordon in both films "Diary of a Wimpy Kid" and "Diary of a Wimpy Kid: Rodrick Rules". However, he will also portray in "Diary of a Wimpy Kid: Dog Days" which will be released in November this year 2012.
He is also a twelve/thirteen year old currently either on the end of Middle School or just participating High School. He writes the Diary in "The Diary of a Wimpy Kid" and along the series.