Cadbury and Blippar showed off their free application -- available for iPhones and most Android devices -- at the ad:tech London 2011 conference.
When the app is running, pointing the phone's camera at a Cadbury countline launches an 'augmented reality' game played by tapping on ducks that appear to emerge from the chocolate bar.
Blippar's makers claim the app could spell the end for QR codes.
"The implications are enormous and we look forward to being at the forefront of delivering compelling experiences for users with other exciting brands,” said Blippar chief executive Ambarish Mitra.
"Image-recognition enabled augmented reality is far from a gimmick and will fundamentally change how consumers interact with their favourite real-world brands."