DVD

DVD was a digital-based physical visual media format used on Earth in the late 20th century and early 21st century.

The information video about Kroagnon that the Seventh Doctor watches appears to be in the DVD format, despite the device having not been invented yet at the time of production. (TV: Paradise Towers (TV story))

Billy Shipton, acting on instructions from the Tenth Doctor decades earlier, entered into the DVD authoring business after plying his trade in video publishing. In the mid-2000s, he arranged secretly to have a specially encoded Easter egg file added to each of seventeen commercially released DVDs.

The file, when opened by viewers, played a one-sided video message from the Doctor recorded in 1969 intended for Sally Sparrow. The message was noticed by Larry Nightingale (who worked in a DVD rental shop) and other Internet forum users before finally being seen by Sparrow herself in the midst of her encounter with the Weeping Angels. Sparrow eventually realised that the seventeen DVDs containing the Easter egg consisted of her complete collection at that time. The Easter egg file served an additional purpose: it transformed each encoded DVD into a special control disc good for a single one-way journey in the Doctor's TARDIS. When inserted into a DVD drive mounted to the control console, it activated the TARDIS and sent it back to 1969 to be retrieved by the Doctor. (TV: Blink)


 * It was not revealed exactly what a viewer of one of the seventeen DVDs needed to do to access the Easter egg.