HONG KONG—A 54-foot tall, bright yellow inflatable duck floating in Victoria Harbor has ignited a frenzy in the city, attracting hundreds of thousands of visitors and spawning a wave of duck-related products and dishes, occasionally served with the famous visitor's feathered brethren.

The duck has already shown up in nine countries, in cities from Osaka to São Paulo to Sydney. But the welcome it has triggered in Hong Kong has eclipsed them all. Residents in the city embraced the inflatable water fowl even before it arrived....