Create a vibrant and slightly cartoonish illustration of Harry Potter and Ron Weasley sitting on the ground at Hogwarts. They should be smiling and relaxed, with their arms resting on their knees. Harry has round glasses, a lightning scar, and messy black hair, while Ron has red hair and freckles. Both are wearing Gryffindor robes. The background features the majestic Hogwarts Castle with its towers and spires, floating candles, twinkling stars, and magical elements like sparkles and tiny creatures. The illustration should be vivid in color and suitable for T-shirt printing.