Board Thread:General Discussion/@comment-25095167-20141115031516/@comment-25831580-20141224022407

Exactly, without CJ in those episodes Rigby and Eileen never get to hang out in Play Date, and Video 101 is not the same without CJ and if it wasn't for CJ visiting Mordecai's parents, he won't learn to respect his mom more. So in conclusion, CJ is an important character.