Chip

Chip was a force-grown clone created by the Lady Cassandra O'Brien to serve her. He appeared to be almost human but with distinctive markings on his skin. Cassandra claimed that she had modelled him on her favourite pattern, a pattern she had seen on the skin of the last man who ever told her she was beautiful. Chip travelled with Cassandra and was onboard her ship on the day the Earth was destroyed in the year 5,000,000,000.

Following Cassandra's apparent death, he went onto Platform One and rescued her brain as well her "pretty blue eyes" which were salvaged from the bin, connecting it to the skin taken from her back. Chip travelled with Cassandra before finding the recently established colony of New Earth. There, the Sisters of Plenitude were engaging in experimentation leading to the rapid development of medical treatment. Chip hid Cassandra in an abandoned section of their hospital in the city of New New York. Cassandra rested there while he stole advanced medicines. His devotion occasionally irritated her. He had an Irish accent. He was referred to by Cassandra as a "walking doodle" when she entered his body before dying.

When the Tenth Doctor and Rose arrived on New Earth, Chip assisted in Cassandra's plans to kidnap Rose and use a psychograft to take control of her body. Despite the fact that she abandoned him to what she believed was a certain death at the hands of the human experiments who were released, Chip continued to worship his creator.

When the Doctor forced her to leave Rose, Chip acted as a willing host even though the transfer of Cassandra's consciousness strained his heart and led to both of their deaths.

The Doctor took Cassandra (in Chip's body) back to a party hosted by the Ambassador of Thrace. She told her younger self that she was beautiful before dying in her own arms. This incident created a predestination paradox that would eventually lead to Chip's own creation in his current form.

Biography from the TARDIS Data Core article, licensed under CC-BY-SA