After participating in an unspecified crime, Duncan was ordered by court sentence to help out at Foster's Home at the time before the invasion began. Although he reluctantly agreed to these terms in order to prevent spending time in confinement, Duncan genuinely cares (at least to a moderate degree) for Foster's and the imaginary friends.Though this is something he has a hard time admitting, he gradually becomes more open about it. He remains at Foster's Home during FusionFall, participating in many missions involving Imaginery Energy and the status of imaginery friends. Duncan can be found by Frankie in front of the house.
During FusionFall, Duncan appears to have since distanced himself from many of his former fellow competitors, both friend and foe. Though he does begin to reignite and revisit many of his old relations during the invasion especially through missions.