Dropas
The story goes that somewhere around 10,000 BC a giant alien spaceship would have crashed in the Himalayas, in a region that is now on the Chinese - Tibetan border. Descendants of the crash survivors would still live there in an isolated tribe. They would be called the Dropas, are said to be human-looking, yet would on average only be 3 to 4 feet tall.
That, at least, is what the book Sungods in Exile would have you believe. The book was published in 1978, by 'David Agamom,' and allegedly was based upon the notes of a Dr Karyl Robin-Evans whom Agamon claimed was a professor at Oxford University. The book tells of a 1947 expedition to Tibet in which the scientist visited Bayan Har Mountains. Robin-Evans claimed that the Dropa tribe was of extraterrestrial origin and had crashed on Earth. The book featured photographs of the tribe and the alleged Dropa stones which contained messages from the extraterrestrials.
From the very beginning, however, there were problems: no Dr. Karyl Robin-Evans could be found. Other characters who were added later to the tale, also turned out to be non-existent.
Then, in 1995, British author David Gamon admitted in Fortean Times that he had written Sungods in Exile as a hoax under the Agamon pseudonym, inspired by the popularity of Erich von Däniken and his books on ancient astronauts. The source material for the story was taken from a 1960's magazine article in Russian Digest, and a 1973 French science fiction novel Les disques de Biem-Kara, (The discs of Biem-Kara), by Daniel Piret.
Other alien 'immigrants' are the Norcans and the Janosians.
Main source of information: wikipedia: Sungods in Exile