He helped the team at S.T.A.R. Labs when he saved Jake from a Symbiote.
He made his first actual appearance after he fought against Saix and revealed himself to the team. He later asked to join and they allowed him.
In the following episode he explains his grudge against Saix when Ben and Knuckles say they don't trust him that much and after a battle against Saix and his Berserkers. After that he gains his friends trust.
He becomes a sort of older brother figure to Jake.