Dr. Who

Perhaps the most famous immortal and time traveler of all in modern literature and on TV would have to be none other than Dr. Who. For nearly 50 years. Dr. Who is a British science fiction television program produced by the British Broadcasting Corporation (BBC). The program originally aired in 1963 starring William Hartnell and continued on with other actors portraying the Doctor to 1989. The show was revived in 1996 as a television film starring Paul McGann, and later relaunched in 2005 and has continued on to this day.
Known simply as the Doctor he is able to travel through time and space inside his TARDIS (an acronym for Time And Relative Dimensions In Space) machine that resembles a blue 1950s British police box. Many of the Doctor's traveling companions have observed that the inside of the TARDIS is larger than the outside. The Doctor operates a Type 40 TARDIS which functions by block transfer equations (Distributed Cluster Algebra) necessary to create a Space-Time Event connected to the Eye of Harmony. Only the Time Lords are able to create a TARDIS, and surprisingly enough, they are not built but rather grown and are quite sentient. The workings of the TARDIS can easily be explained using modern mathematics and Four Dimensional Engineering.

Dr. Who is humanoid, eccentric, clever, heroic, and virtually immortal, and estimated to be over 900 years old. (Methuselah in the Old Testament of the Bible, grandfather of Noah who built the "Ark" is said to have lived to be 969 years of age.) The Doctor claims to be an alien who can regenerate his body at least a dozen times whenever his body is fatally damaged. Unbeknownst to his traveling companions the Doctor has reincarnated into a new body several times already throughout his life with most of his memory intact. With each new regeneration that occurs the Doctor's characteristics change and develop into a new personality that is similar and yet different from the one before.

The Doctor travels through space and time in and out of history and future-history, fighting injustice and battling an assortment of foes. In one particular storyline Doctor Who is said to have been the incarnation of Merlin in another timeline. The same mysterious magician Merlin, who had incredible knowledge, was the master of time, and thought to be immortal. The Doctor reluctantly acknowledges that it could indeed be him from the far future traveled back to ancient times to aid King Arthur and his plight.

The Doctor comes from a race of Time Lords whose civilization and technology has made them masters at manipulating time and space. It is said that Time Lords can live "practically forever" barring accidents, and that in some extreme cases, they will use the elixir of life. When regeneration is not possible, using the elixir of life will grant them a chance to live longer yet again.
Time Lords were legendary throughout the entire galaxy and known to be godlike beings who could master time and space. Dr. Who is known to have two passions in life: One is his freedom and the other is his fascination with the planet Earth. His love for humans is well known and he will protect them even at the cost of his own life. Much like the mythological hero Gilgamesh, the one who has never tasted death.....the Doctor is a hero who strides through the centuries....ultimately alone."
Dr. Who is undoubtedly a hero and has been played on BBC TV by 10 gifted actors already since 1963. Dr. Who gained fame in the United States in the 1970s, when Dr. Who was portrayed by the very popular Tom Baker. His portrayal of the Doctor has been the longest and the most eccentric version of the Doctor's characteristics. Currently the Doctor can be seen on cable stations across America and in other countries around the world. The tenth incarnation of the Doctor was recently played by David Tennant who has successfully passed the role to Matt Smith in 2010 as the eleventh Doctor.