Avengers: Age Of Ultron - 32 Easter Eggs, In-Jokes And References
32. The Source Comics
Despite the name, there's very little of the original Age of Ultron comic in the film - the name was simply chosen because it sounded cool. It's more based on an amalgamation of comics.
Ultron's origin comes from Avengers volume 1, issues 54-58 and the Twins as terrorists who heel turn to join the Avengers comes from Avengers #16, and the characters are closely based on the Marvel Ultimates iterations. There are also elements of the killer AI Sentient Armor story-line (Iron Man vol.3 #26-30), and Ultron's multiple bodies and upgrading comes straight from Ultron Unlimited.
Additionally, Joss Whedon admitted that both The Godfather Part II and Star Wars Episode V: The Empire Strikes Back were major inspirations for the film.