Shada was an episode of the classic Doctor Who series. It was an episode that starred Tom Baker as the 4th Doctor. Due to a strike at the BBC, production of this episode was halted, and never completed. Footage from this episode was then used in the 20th anniversary special of the show, 'The Five Doctors.' In this episode the 4th Doctor became trapped in time, before being returned to Earth.

Several years later, the episode was released on VHS, along with linking narration from Tom Baker, to explain the bits of missing footage.

Now, several years ago, Shada was remade as a Big Finish audio drama starring Paul McGann as the Doctor. And then this was remade as a BBC animated webcast. The Paul McGann version explained that after the 4th Doctor was returned to Earth in 'The Five Doctors' he went on his next adventure, without doing what he originally intended to do on Earth. The 8th Doctor wants to continue that mission.

Neither of these adventures is considered 'canon.' And also, neither of these adventures have been released on DVD.