The Doctor was a Time Lord, and like the Beginner fled from Gallifrey. His TARDIS crashed into the Beginner's TARDIS when he was fleeing, causing his TARDIS to stay in the shape of a police box. (Encounters)
Chronologically in the show, the first encounter of the Beginner and the Doctor was in World War II, however they see to share some history prior to this moment. The Doctor's TARDIS is stuck on a roof, so the Beginner takes him to where the TARDIS was last at before landing during the Blitz (The War and the Time Crack).
Landing in Rome, the duo encountered the Rock Kind, and a roman guard who was guarding the Doctor's TARDIS. The Doctor was sent back to his time of 'death'. (TARDIS in Rome, The Impossible Astronaut, The Wedding of River Song).
Behind the scenes Edit
Beginner's Adventures is a spin-off based on the hugely successful and popular show Doctor Who, where the Doctor is the main character of the show.