Allegedly somewhere around 10 000 BC, a giant alien space ship had crashed in the Himalayas, in a region that is now on the Chinese-Tibetan border. Descendants of the crash survivors still live there in an isolated tribe. They are called the Dropas, and are said to be human-looking, yet on average only 3 to 4 feet tall.
Other alien 'immigrants' are the Norcans and the Janosians.