According to Joss Whedon, he’s having quite the time with a particular robot who will prove quite the adversary for The Avengers. "I'm having a blast with Ultron," Whedon said. "He's not a creature of logic - he's a robot who's genuinely disturbed. We're finding out what makes him menacing and at the same time endearing and funny and strange and unexpected, and everything a robot never is."
Speaking to Empire magazine the writer / director went on to say that the Avengers 2 will be very different."The number of different looks and textures and moods we're getting from the British locations is stupid awesome, because this, palette-wise, is very different. I'm trying to make a different film. Because why would you make one movie twice? That seems weird."