River Song

SPOILER ALERT!!!

River Song is the daughter of Amelia Pond and Rory Williams. Her original name was Melody Pond, but she changed her name to "River Song", which originated from a gift a young army girl from the Forest of Cheem gave to Amy. The girl sewed the name of Amy's daughter onto a star, but the only water in the forest is the river, so "Melody Pond" was translated into "River Song."

The Impossible Astronaut

She liked flirting with people (especially the Doctor), saying "Spoilers!" and "Hello Sweetie", and leaving messages throughout space and time for the Doctor. She often carried a gun, and used hallucinogenic lipstick to get her way. She also had a thing for shooting hats (even cool ones) off the Doctor's head.

River was born in a place called Demon's Run, and captured and raised by the Silence to kill the Doctor. Because she was conceived in the TARDIS, she is considered a child of the TARDIS, and those in Demon's Run were able to manipulate her DNA so that she became half Time Lord.

As a child, she was frightened of what she said was "a space man trying to eat her", so she called the president of the United States and gave her exact location. The Doctor helped to investigate this and discovered the the space man (which was really just an empty spacesuit), already had eaten her. Later, she managed to force her way out.

Having no memory of this incident, she then regenerated in an alleyway. She tracked down her parents and grew up with them as their best friend, "Mels" but they did not realize she was their daughter.

Later she pointed a gun at the Doctor and forced him to take her on the TARDIS to "kill Hitler". She was accidentally shot during this encounter where she then regenerated into the form that would later become River Song. She attempted to kill the Doctor and would have succeeded, had she not fallen in love with him and kissed him, giving him all her regenerations to save his life.

Soon after this, she decided to become a doctor of archeaology, trying to find the Doctor. Unfortunately, the Silence found her and forced her into her old space suit again. She then became the Impossible Astronaut who rose from Lake Silencio to kill the Doctor.

Instead, she managed to save him, but in doing so changed a fixed point in time. This caused time to freeze and begin deteriorating. As the Doctor put it, "Nothing happened. Or everything happened at once, if you prefer." 

The Name of the Doctor

The Doctor then revealed to River that even if she shot him, he wouldn't die, so they kissed, and their touch started time up again. River supposedly killed the Doctor, but in truth he survived. 

River then went to prison for a murder that she never remembered doing. Stormcage, however, could not contain her, and she could slip in and out of her cell without any sort of problem. She never agreed to become a full time companion, but she accompanied the Doctor on many adventures, including the Crash of the Byzantium, Dinner at Asgod, and when the Pandorica Opened. 

Eventually, she arrived at the Library, where the Doctor met her for the first time. Here she sacrificed her life to restore all the people who were "saved" in the Library's computer database.

Her final adventure (to date) was when she, only a projection or something saved in the Library's computer accompanied the Doctor and his companion Clara to Trenzalore, where the Doctor was buried in the episode The Name of the Doctor.