In "Thoughtscape", the Jonny and Doctor Quest are subjected to their worst nightmares in Questworld. For Doctor Quest, it's the idea that Jonny, Jessie, Hadji, and Race all died because he failed. Jonny is subjected to the image of his father cruelly dismissing him for being less interested in the sciences than Jessie, and for being an utter disappointment. Cue the real Doctor Quest showing up before Jonny can go over the Despair Event Horizon.
Dr. Quest: Disappointment? Nothing could be further from the truth!