1. An entertainment device, comprising: a display generator arranged to generate for display a representation of an on-line virtual environment, that on-line virtual environment being able to host interactions between a user of the entertainment device and other users of one or more remote entertainment devices; a network communications arrangement operable to receive data representative of the actions of the other users within the on-line virtual environment, and operable to receive data indicative of any supplementary data files interoperable with the on-line virtual environment that are associated with one or more remote entertainment devices of users who join the on-line virtual environment; a data file searcher operable to search the entertainment device for any supplementary data files indicated by the received data; a data file acquisition arrangement operable to acquire, from a networked device, a copy of a supplementary data file indicated by the received data that was not found on the entertainment device; and a data file integrator operable to incorporate relevant elements of the or each supplementary data file into the representation of the on-line virtual environment.