Second Doctor (clone)

The Second Doctor was a clone created from the Fourth Doctor. He had the Doctor's real memories, and indeed thought he was the Doctor. The Fourth Doctor met him and proved his false identity, but not before Hexiford was moved into space, and The Shiscari infant nearly devoured him. The Fourth Doctor said that due to his cloning type, he would not live mote than a few mounths. (AG: The Hexford Invasion, Survivors in Space)