One show that does a great job with diversity in general, including body shapes is Caillou (KI-yoo). Caillou's friend Leo is stocky and happy and active. He is Caillou's best friend. He is not depressed or sad, he is not shown compulsively eating, he is not lectured about 'good' and 'bad' foods. He's just Caillou's best friend. Caillou's mother wears baggy sweaters and doesn't have lip-liner or fake lashes like Bratz dolls do. Caillou's teacher shows up in a swimsuit with a normally ample body shape in a one-piece suit! No bikinis with cleavage. Its just not an issue.
Its refreshing and important in an era when four-year olds already show signs of body dissatisfaction and self-loathing. Check it out!