The script held in the Crawford Collection in the AFI Research Collection contains the following character notes (excluding regular characters):
'HARRY THOMAS: 30 years old. But mentally he's about 10. He looks normal enough, but when he speaks we see and hear the child. Harmless.
'JEFF DAVIS: 12 years old. A quiet, friendly boy and a diabetic. When he meets up with Harry, he understands Harry's need for a friend.
'TIM BENSON: 12 years old. Mischievous, always in trouble, without really meaning any harm.
'BOBBY CLARK: 12 years old. He's very like Tim and follows him in everything, they're buddies.
'MRS. JUPP: 45 years old. A sour faced woman. The Thomas' neighbour, not happy.
'MRS. DAVIS: 30 years old. Hardworking, pleasant woman. A little too easy going with Jeff perhaps.'