Harry was a talented artist and storywriter, so good that the universe was inspired to create things based on his imagination, such as the Xarantharax and Iska'lanz'rm races. In December 2008, he met the Tenth Doctor, who was dressed as Santa Claus in a local shopping centre. He gave Harry a TARDIS key, telling him that he would need to use it one day. Harry later met Martha, who was posing as a shop assistant. She gave him blueprints to the TARDIS console, telling him that he would also need these. They were then attacked by a Xarantharax, whom Harry attacked with perfume.
Early on Christmas Day, Harry sneaked downstairs and found a present much larger than any other. He unwrapped it, revealing the TARDIS. He opened the door using the key, then followed the instructions on the blueprints, which caused the TARDIS to materialise in space above a war. Harry recognised that this was the war he had created between the Xarantharax and the Iska'lanz'rm. The TARDIS then took him to his school, where he met his teacher. She revealed herself to be an Iska'lanz'rm and attacked Harry, telling him that he must not draw the TARDIS onto the picture he had drawn of their war. The Doctor and Martha arrived and he drew the TARDIS in the scene, causing the Xarantharax and Iska'lanz'rm to travel back to their homeworld and agree to peace. (PROSE: The Box Under the Tree)