So he went up into the hills and mountains in New Zealand, where the Rings movies were made, and stayed on his own.
"Gollum is possessed by the ring, so it is a very physical role," Andy said. "It has taken so much out of his body, that he literally crawls around all the time."
When Andy first auditioned, it was just to provide the voice of Gollum, who was going to be a computer-generated character. But director Peter Jackson was so impressed with him that he decided to make Gollum semi-human.