Methods, units and systems for rendering data streams in devices, for example, toys. In one aspect, the method for rendering a time-dependent data streams in a device may comprise: storing in the device at least one time-dependent data stream, the data stream comprising at least one segment of data, each at least one data segment comprising a data stream to be rendered by the device and at least one segment descriptor, each at least one segment descriptor providing information for rendering the data stream of the respective segment and; start rendering by the device a stored at least one segment, following an event, the event related to information in the at least one segment descriptor and; rendering at least one segment in accordance to information in the descriptor.