Character Analysis
Okay, so that's not actually his name (we don't learn his real name), but that's how David depicts him. He's David's therapist, and although he's only in one brief scene, his presence changes everything. When David first goes to treatment, the White Rabbit asks:
"A boy who has had cancer… a boy whose parents and doctors did not tell him he had cancer… a boy who had to find out the truth on his own… is this crazy?" (4.34)
Why yes, Doc, yes it is. But this is the first time anyone's acknowledged this about David's life—the first time anyone's validated that some things about his childhood have been seriously off. When David doesn't answer the doctor's questions, the White Rabbit says:
"I'm going to tell you the truth, […] your mother doesn't love you." (4.38, 43)
This might seem like the worst thing a therapist could say to a patient, but in David's case, it's exactly what he needed to hear. Finally, somebody has been honest, and the Rabbit think this is the key to helping David heal. And the Rabbit, of course, is right.