If you haven't seen Age of Ultron don't read on because there are SPOILERS. If you have seen this awesome film then feel free to scroll down.
So. Long before Avengers Joss created Buffy The Vampire Slayer, a show about a funny blond girl who stakes vampires and saves the world "a lot." If you haven't watched this show and are a Joss Whedon fan then stop reading this and go watch it. For those of you that have watched it you may remember a certain episode called "I Robot You Jane" (Season 1, episode 8). I watched this episode again the other day shortly after seeing Age of Ultron and was very surprised by the similarity's between these two Joss Whedon creations.
The episode starts with a flashback where a demon Called "Moloch The Corrupter" gets trapped inside a book where he is stored as a load of letters in a very old language. Later in the episode the character Willow scans these letters into a computer attempting to keep a digital record of the book, inadvertently releasing the demon into cyberspace!
Now this is very similar to Stark and Banner finding a load of data inside the mind-stone, uploading it into a computer system and inadvertently releasing Ultron into cyberspace. Not only that but both Moloch and Ultron have the same first words when this happens. "Where am I?"
Moloch then goes on to seduce the IT savvy school pupils for his evil schemes including Willow who is a red headed witch in the Buffy series. Ultron also managed to recruit followers including a certain woman associated with the color red and witchcraft.
It takes Buffy and her Scooby gang a while to work out just what the hell's going on meanwhile Moloch is rewriting everyone's school reports to say that Hitler's reign was an example of a well ordered society and other such mischief, displaying the same extreme utilitarian world views as Ultron. When Buffy and co eventually do work out what's happened they express all the same concerns that the avengers had about Ultron. Worries such as Moloch destroying the economy, accessing nukes and so on.
So, what happens next? Well of course Moloch has his human minions build a big metal body complete with red eyes and a dead pan sense of humor... just like Ultron!
Willow by this point had turned against Moloch but was kidnapped by his minions and had a chat with him while he broke a few people's necks then Buffy turns up ready to fight. During their fight Moloch is forced out of the net and trapped in his metal body. Which is exactly what happened to Ultron (granted Ultron had multiple bodys to run around in at this point) but still this is remarkably similar.
Then the whole of Sunnydale floats in the air and the film ends with him and Vision having a chat. Ok that's not true, no flying citys or Vision, he's beaten up by Buffy and electrocutes himself on a wall panel. I'm not saying this is exactly the same as Age of Ultron but there are similarities and it's a pretty cool connection. I wonder if Whedon's mind wondered back to this episode at any point while he was working on Age of Ultron.