April and Bobby both disappear in couple shots when Brenda asks Little Bill what happened after drawing on April's door.
When Little Bill is at the hospital listening to Dr. Clinkscales heart, the stethoscope is around his neck, but in the next shot of Dr. Clinkscales when he gets the X-ray results from the nurse, the stethoscope appears back around Dr. Clinkscales neck when he thanks her for the results.
When Little Bill is imagining playing basketball with the basketball lady, his arm is not in the cast, but as his imagination ends and accidentally draws on April's door, his cast is back on. This was just a fantasy sequence, since Little Bill was just imagining being able to use that arm.