Marvel has announced that for 2015's [The Avengers: Age Of Ultron](movie:293035), the main antagonist will be receiving a new origin story. After watching all of the movies (up to date) in the Marvel Cinematic Universe, I have developed my own theory for how Ultron will be brought into existence.
First, so no one get's confused, lets start off with Ultron's original origin story.
Ultron first appears in Avengers #54 (1968) The character leads the Masters of Evil against the Avengers, having hypnotized Edwin Jarvis into working for him. Flashbacks reveal that Ultron is the creation of Henry Pym, and based on Pym's brain patterns. The robot gradually developed its own intelligence and rebelled, and almost immediately develops an Oedipus Complex, whereby it feels irrational hatred for his "father" Hank.
Now, since Marvel Studios revealed that Ultron's origin would be altered, many fans speculated Tony Stark would be playing a role in his creation. However, I've created my own theory.
After seeing Captain America: The Winter Soldier, and realizing that Hydra has been working within SHIELD since it's creation, I determined that Ultron would be created from Hydra, however, not originally. Michael Douglas has been cast as Henry (Hank) Pym in 2015s [Ant-Man](movie:9048), alongside Paul Rudd as Scott Lang. With this casting, I've speculated that Hank Pym, being an older fella, has been affiliated with SHIELD since it's creation. In order for Marvel to stick to the original story with just a slight change, I think they should follow this lead.
Several years after the death of Captain America, Hank Pym and Howard Stark begin constructing new mechanical soldiers for the United States Army. However, due to expenses the operation is canned and locked away. Fast forward to modern day, where SHIELD has now shown itself to secretly be Hydra. Baron von Strucker, who we see in the mid-credit scene of Captain America, has his hands on many SHIELD crates that were unused or stolen. While looking through the crates von Strucker finds what looks like a 1950's version of Iron Man. Using stolen SHIELD and Stark technology *cough cough JARVIS* Von Strucker upgrades the machine and powers it using the mind gem in Loki's scepter (last seen in Strucker's possession in The Winter Soldier) Finally, Hydra upgrades Ultron with his infamous vibranium shell, which was in SHIELDs possession since Captain America: The First Avenger.
What do you guys think of my theory? Comment below :)