John "Jack" Pappas is the son of Mr. Pappas and Didi Stone. He is one of the main characters and was the team captain and quarterback for Grant High School's football team. It is revealed that he eventually got married to Madison Pappas . He is portrayed by Greg Finley.
Jack and Adrian had oral sex, so Grace broke up with him. His former girlfriend is Grace Bowman. Towards the end of season 1, he turns himself in for making fake IDs to help cover his friend. He is assigned to do mentoring to a 14-year-old named Duncan and finds he has an interest in his 20-year-old sister, Shawna.
In Season 2, Jack and Grace then rekindled their relationship. At the very beginning of the season, she had sex with him as an attempt to "keep him", but when her father died the same night, she pushed him away. Grace eventually accepted her father's death and got back together with Jack.
Over the summer, Grace was away at doctor camp and since she would no longer have sex with him, Jack cheated on her again with Madison Cooperstein. This led to the end of their relationship.
It was revealed in the episode Girlfriends by Amy Juergens that Jack and Grace will apparently go over to Amy and Ricky's apartment for dinner. There it is revealed that he had sex with Clementine. In the episode Property Not For Sale, the hooker Ginger enters his dorm room to offer herself and Jack ends up helping her to get back with her real family and escape her pimp.
In the episode Regrets, Jack gets beaten up badly by Pimp for giving money to his hooker in order to escape from him. He is in critical condition, has surgery and is in coma for months. In the episode Hedy's Happy Holiday House Jack wakes up from coma.