The Eleventh Doctor is the eleventh incarnation of the Doctor, a time-travelling Time Lord. After absorbing a vast amount of nuclear radiation, the Tenth Doctor regenerated in his TARDIS. The energy released caused great damage to the vessel. Focused initially on his new form, he did not immediately realise the TARDIS was on fire and about to crash. When he did, he seemed to enjoy the thrill of the moment, gleefully shouting, "Geronimo!", as his TARDIS plummeted to Earth.