A networking system comprises a data communication network, an entertainment device operable to communicate over the network and to run a first application, a social networking server operable to supply a second application to a social networking client over the network, the client being operable to run the second application once received from the server. In response to a first predetermined event during operation of the first application, the entertainment device can communicate an alert message to the server identifying a user of the client to receive the second application. The social networking server is arranged to supply the second application to the client in response to the alert message. In response to a second predetermined event during operation of the second application, the client is arranged to communicate an acknowledgement message to the entertainment device. In response, the entertainment device is arranged to modify operation of the first application.