At this point, let's just start making lists of longtime friends of Robert Downey Jr. and assume that they're all going to wind up in Marvel Movies eventually. James Spader has been cast as ULTRON for "Avengers 2." Newsworthy in and of itself, definitely, but interesting because it highlights the fact that there's a lot more mystery this time around.
The only "secret" in the first "Avengers" was what the aliens were going to be called (and that still seems more like the result of Marvel going into production without actually knowing what name/design they were legally allowed to use since these were clearly supposed to be Skrulls at one point); but since it's already been confirmed that the movie Ultron will have a different origin (in the comics he's a rogue invention of perennial super-science fuck-up Hank Pym, aka "Ant-Man" whose movie isn't due out until after A2) this is that rare moment where longtime fans aren't really ahead of the game as to what the story of a Marvel Studios production is going to be (no, "predicting" that "Avengers" would go "meet, disagree, make up, smack the Putty Patrol around NYC" doesn't count.)
Hit the jump for some crazy theories:
Ultron's origin in the comics is a bit convoluted: He first shows up as a masked mystery-villain, then reveals himself to be a humanoid robot, then reveals that he's a self-improving, artificially-intelligent machine that originated as an early stab at sentient robotics by Dr. Pym that went nuts (Oedipus Complex - he hates his "father" and is obsessed with Pym's then-girlfriend Janet Van Dyne aka "The Wasp") and ran off to go become evil.
The announcement-teaser shown at SDCC was an extreme-closeup of what looked like a new Iron Man helmet under-construction, zooming out to reveal Ultron's face at the very end. That started what's probably the easiest "call" to make guessing-game wise: With no Ant-Man on the scene, Ultron's creator will probably end up being Tony Stark (in comics, Ultron It makes the most sense, and it's not like Marvel would be against having more things in these movies lead back to Iron Man. One of the Iron Man armors gets a mind of it's own? That's not a bad new origin, and as good a way as any to get Stark back into the game after he more or less (SPOILER ALERT!) decides to dial back on the Iron Man-ing at the end of "Iron Man 3."
The fun conclusion jumped to next: The "A.I. gone bad" mind inside Ultron will be J.A.R.V.I.S., Stark's personal A.I. voiced in all the movies thus far by Paul Bettany. That'd be a cool twist and a novel use of the shared-universe conceit (minor character from one series becomes a big bad in the team-up ten films later), and hypnotizing the human-butler version of Jarvis was part of Ultron's debut story in Avengers #68, but with Spader now confirmed as the voice (and probably fake-human "face," at least some of the time) of the character that theory seems to be out the window.
Or is it? I've got a theory of my own: Very silly, kind of crazy, pretty unlikely but not 100% outside the realm of possibility:
What if Ultron is DUMMY?*
As in "Dummy," the semi-self-aware robotic arm that Tony Stark keeps around for menial tasks, treats like the world's dumbest robot dog but also seems to have some kind of sentimentality about (he's one of the few things being taken away from the ruins of Stark's house in IM3)? It's already been established, after all, that Dummy is more-or-less the precursor to J.A.R.V.I.S. and all Stark's other robot/robot-esque projects...
...so it'd make a nice retrofit of the comics' origin (and maybe another chance to give Pepper Potts something to do in an "Avengers" movie, something RDJ insisted on in the first one.) And if you're looking to send audiences home with some kind of lingering "whoa," the idea that a comic relief background player from "Iron Man" turns into a dangerous villain more-or-less because of all that abuse we were laughing at would do it - plus, you KNOW that Downey's "...DUMMY!??" reaction would be fucking priceless.
Ultron the Big Scary Terminator-Esque Robot is giving his big "Reap what you sow!!!" self-justifying villain speech, an instead of flashing back to a war-zone or some childhood trauma it's just scene after scene of RDJ being a dick to a robot arm? GOLD. Potential subsequent related dialogue? ("I yell at my microwave at least once a day and it never tried to take over the world or kill me! ...well, okay maybe that one time.") Solid.
Realistically, this is pretty damn unlikely - mostly because it it might be a little too far over the line between "good silly" (re: Thor) and "too silly" (re: Frog Thor,") but I'd be all over it. Meanwhile, I wouldn't count J.A.R.V.I.S. out as having a bigger role in a robot/AI-related story: If both Ultron and Scarlet Witch are in this, it'd be really surprising if The Vision didn't turn up as well.
*Just so we're clear: If it turns out I'm even half right about this, I'm never ever shutting up about it.