Dr. Gross is Dr. Cox's therapist.
Although Dr. Cox doesn't believe that therapists are "real doctors", he still sees Dr. Gross for therapy. He complains every time about how much of a quack he thinks Dr. Gross is, until one day Dr. Gross tells him that he doesn't want him as a client anymore. Dr. Cox takes some of his advice and listens to some advice J.D. gives. After doing this, he tracks down Dr. Gross at a restaurant and reveals his embarrassing admission. Dr. Gross tells Perry to keep whoever gave him the advice in his life and walks out of the restaurant. ("His Story")