India’s favorite girl never grows up. But her wit is less welcome.

MUMBAI — Nearly two decades after India’s independence, a little-known cooperative of small-town dairy farmers in 1966 launched what became the most successful advertising campaign in the country’s history and helped transform India into the world’s largest producer of dairy and dairy products.

The economic business model developed by Amul, the dairy cooperative, spread throughout India, as did its cartoon advertising mascot: a young girl with blue hair, a polka dot dress and an endless stream of witty one-liners commenting on the events of the day. The girl quickly became India’s most recognizable cartoon character, a cultural icon that spared no public figure.