The friendship between Jo and the Doctor had developed very quickly, and it was quite obvious Jo was the right companion for him. He was rather bad-tempered and insulted people quite a bit, but Jo was, at times, able to calm the temper with her sense of humor and wonderfully silly personality. In the beginning, Jo started off shaky, but as the stories went on, the character of Jo seemed to develop even better. Katy Manning seemed to being growing into her character more as well. She honestly worked the best with the Third Doctor because she was quite the opposite. Liz Shaw for example, was far too scientific, and couldn't challenge the Doctor enough. Sure she could be doubtful of his theories, but if he had her help with research or go look at the evidence, well she could scientifically think of ways of how and why things happened. Jo was not like that. She asked questions, and she helped in different ways. She also seemed more accepting of his theories and answers compared to other companions.