Entertainment Weekly unveils Ultron’s Origin in the film:
For better or worse (trust us, itâ€™s worse), his Tony Stark has devised a plan that wonâ€™t require him to put on the Iron Man suit anymore, and should allow Captain America, Thor, Black Widow, Hawkeye, and the Hulk to get some much needed R&R as well. His solution is Ultron, self-aware, self-teaching, artificial intelligence designed to help assess threats, and direct Starkâ€™s Iron Legion of drones to battle evildoers instead.
The only problem? Ultron (played by James Spader through performance-capture technology) lacks the human touch, and his superior intellect quickly determines that life on Earth would go a lot smoother if he just got rid of Public Enemy No. 1: Human beings. â€œUltron sees the big picture and he goes, â€˜Okay, we need radical change, which will be violent and appalling, in order to make everything betterâ€™; heâ€™s not just going â€˜Muhaha, soon Iâ€™ll rule!â€™â€ Whedon says, rubbing his hands together.
â€œHeâ€™s on a mission,â€ the filmmaker adds, and smiles thinly. â€œHe wants to save us.â€
So instead of J.A.R.V.I.S. becoming corrupt, Stark creates Ultron and then presumably gives J.A.R.V.I.S. a body in the form of The Vision.