In "Supplies Party", Chad overused the word "stupid", against Adam and reminded him of when he wet his pants and cried at his 6th birthday party. At Adam's 12th birthday, the same thing happened and Chad laughed at him, yet again.
In "The Times, They Are Exchangin", Adam went back to CAMS and had another encounter with Chad.
In "Human Behavior", Chad was one of the feral students at the CAMS dance.
In "Lonely Lyon", Chad missed bullying Adam and wanted him to come back to CAMS. So, he forged a complaint from Adam, wanting to leave CDMS and go back to his old school, as part of an elaborate scheme to get him back. Principal Pixiefrog busted him and found out he was also going in disguise as Bear Ted, in attempt to find some way back into Adam's life.