Why does Mario's grandfather call the chair 'special'?
Mario's grandfather calls the chair 'special' because it has the magical ability to reveal who Mario's real friends are.
When Mario manages to sit on the invisible chair, the magic works and shows him that true friends are those who care for him and support him, not those who laugh at his difficulties.
Explanation
The chair is special because it serves as a test to distinguish between real friends and mere companions. The magic of the chair reveals that true friends are those who help when someone is struggling, while false friends merely enjoy watching others fail.
Solution Steps
The chair has a magical ability to reveal who Mario's real friends are
True friends are those who care for him and support him, not those who laugh at his difficulties