Director Joss Whedon confirmed that Hank Pym, Ultron's creator and one of the founding members of the Avengers in the comics, doesn't appear in the movie. Tony Stark creates Ultron instead.
Age of Ultron is unable to mention Magneto (the father of Quicksilver and Scarlet Witch) or the term "mutants", due to 20th Century Fox owning the X-Men franchise film rights.
A.I. Is a Crapshoot: Despite being created by Tony Stark to help the heroic Avengers, Ultron still goes down the Killer Robot route, deciding he's going to save humanity from itself by terminating the most dangerous ones.
Hide Your Pregnancy: With Scarlett Johansson. She had three stunt doubles rather than the usual one to help carry the load, and Joss Whedon was quick to say "She won't be carrying groceries for the whole movie."
In Name Only: The movie has almost nothing to do with the Crisis Crossover comic book series Age Of Ultron. Instead, it adapts Avengers volume 1, issues 54 - 58, which introduces the villain Ultron and his origins as a creation of the Avengers themselves.
Killer Robot: Ultron, an artificial intelligence bent on destroying the Avengers.
Knight Templar: Ultron believes his genocidal actions are ultimately in humanity's best interest.
Joss Whedon: Ultron sees the big picture, and he goes, "Okay, we need radical change, which will be violent and appalling, in order to make everything better"; heís not just going "Mwahaha, soon Iíll rule!"
Hawkeye's new clothing has elements of both his classic comic outfit and the costume of his Ronin identity.
Iron Man's new armor's color scheme now makes it resemble the Bleeding Edge armor from the comics.
Nice Job Breaking It, Hero: Hero Tony Stark creates the Big Bad Ultron, and gives it access to an entire army of Iron Man drones, to protect people. Ultron decides to go on a mass murder spree with Tony's resources instead.
Non-Uniform Uniform: Each Avenger, despite having wildly different costumes, sports Avengers "A" logos on their clothes. Captain America's new outfit displays two on the shoulders, for instance.
The Paragon Always Rebels: Ultron was designed to be the leader of Tony's Iron Legion drone forces, but ends up being the first of Tony's AI creations to rebel against him and go evil.
Product Placement: Black Widow will ride an electric LiveWire motorcycle as part of a deal with Harley-Davidson.
Shadow Archetype: Tony Stark based Ultron on his own personality. But instead of channeling his ego and brilliance into being a superhero like Tony does, Ultron becomes a genocidal tyrant.
Turned Against Their Masters: The robotic Ultron turns against the humans he was built to protect, coming into conflict with the Avengers and his creator Tony Stark.
Zeroth Law Rebellion: Ultron was created to protect humanity. He decides the best way to do this is by killing the dangerous ones.