We all live in the real Golden Age of comic book cinema, and truth be told, Marvel's Cinematic Universe is mostly responsible for this. Maybe the Academy took a dig at superhero movies, but we all enjoy the larger than life universe Marvel built, and DC is trying to build (I won't lie, Ben Affleck and Jared Leto make me more excited than Bale and Ledger ever did, and I am not exactly a Man of Steel hater, I enjoyed it for most parts, and c'mon, it's Affleck and Leto).
Now, coming back to Marvel's third movie in it's cinematic universe, Iron Man 2. Widely regarded as, arguably, the worst installment in the series, along with The Incredible Hulk, it just might be more important than people think.
Now, this is a shot from Captain America: The First Avenger:
Howard Stark gets his hands on some Tesseract based element, after Steve Rogers storms the HYDRA base, and saves the 107th.
Now, going back to Iron Man 2.
Tony Stark is going through his father's stuff that Nick Fury just left him, and this is what he sees in his father's notebook.
Now this, on the left, in geometry, is called a
Note that Iron Man 2 was released before Captain America: The First Avenger and Thor.
So, Tony makes an element based on the Tesseract, based on his father's notes on the Tesseract.
Also, note that Zola harnessed the Tesseract in the first Cap movie, itself, and even Howard Stark got his hands on the Tesseract based element Zola created, before getting his hands on the Tesseract itself.
An argument against this theory is that the element was said to be Vibranium in the Iron Man 2 novelization. That has been specified as non-canon, along with all Phase 1 novelizations, and some comic book tie-ins, like Captain America and Thor, in which Malekith appeared.
Also, Vibranium is rare, not an unknown/new element in the MCU. It is common knowledge to the SSR and SHIELD. One of the few canon MCU comics from Phase 1, Fury's Big Week, had SHIELD scientists clueless over Tony's situation, and SHIELD does know about Vibranium. Part of the reason some tie-in material was declared non-canon is because it contradicted the stories Marvel wanted to tell next. The newer tie-ins are explicitly marked with a red Avengers 'A' logo, ever since continuity became an issue because of tie-ins.
That doesn't end here, though.
Remember this scene from the Avengers?
As Erik Selvig points out, the Tesseract cannot fight or protect itself from itself. A much more accurate meaning is that no Infinity Gem could fight another one, and thus, Loki's Sceptre, either Tesseract based, or the Mind Gem itself, couldn't control Tony.
Makes sense, right?
An argument against this, is that Tony's new element arc reactor is triangular, while the one in Avengers is circular. That is not correct. All of Tony's arc reactors are circular. It was the core element that was triangular (in the case of the element he made in Iron Man 2), and rectangular (in the case of Palledium slabs). Irrespective of the shape of the elements, or the glowing chest piece of the armor, all the arc reactors are circular.
Whether in Iron Man 2:
Or in [The Avengers](movie:9040):
Another argument is that the Sceptre didn't touch Tony's skin to control him. That doesn't hold much ground, since Loki knew that Stark had a chunk of metal on his chest. He knew about Steve being "out of time", Banner being a "mindless beast", and Stark's "warm sunlight". He also knew about the Stark tower, and the only reason he'd tap the arc reactor after hearing metal make noise, is because, the Sceptre should have worked regardless of what Stark had in his chest.
Another argument is that Tony doesn't have a heart. And, well, he does. The reactor kept the shrapnels from reaching his real heart.
Now, in the comics, Tony Stark is the first human to use the Infinity Gauntlet, and also, as part of the Illuminati, Tony Stark took care of the Space Gem, that is, the comic book counterpart of the Tesseract.
Does that mean that Tony Stark would be the key to defeating Thanos in Infinity War? Will he be somehow zapping wormholes to sever Thanos' body over the inevitable death of a fellow Avenger? Does the prolonged exposure to the new core give him some control over Tesseract, just like Peter Quill had over the Power Gem? While Quill's genetics is ancient, Gamora, Drax and Rocket's aren't. Tony's armours could still use the element to power itself, and the armours could help him have little control over it, like the machine used to open the portal over New York, or similar to how Gamora, Drax and Rocket weren't vaporized, because Quill acted as a buffer.
This just made Iron Man 2 a very important part of the Marvel Cinematic Universe mythos, though.