The Doctor is a Time Lord who travels in his space-time-ship Tardis (Time And Relative Dimension In Space). The Doctor is an alien, from the planet Gallifrey. At first he travelled only with his granddaughter. Later the Doctor took other people with him, who are usually called companions or assistants. The Doctor and his companions travel through space and time, have a lot of adventures, and often save many people. His current companion is Amy Pond. Because of an error in its chameleon circuit, the outside of the Tardis always looks like a 1960s-style British police box. The Daleks are one of the most powerful races in the Doctor Who history and are the Doctor's worst enemies. They cry "EX-TER-MIN-ATE!" when they are about to kill someone.