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 an avatar of a user of the entertainment device and avatars of other users of one or more remote entertainment devices, the entertainment device and the one or more remote entertainment devices holding in common code to represent the on-line virtual environment; a network communications arrangement operable to receive data representative of the interactions of the other users within the on-line virtual environment, and operable to receive data indicative of any supplementary data files comprising a modification to be applied to the displayed on-line virtual environment, to represent the avatar of one or more remote entertainment devices of users who join the on-line virtual environment, said supplementary data files comprising one or more graphics textures; 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.