Because Ultron was described as 8-9 feet tall, James Spader had to wear an antennae-like contraption made out of a thick piece of wire with two red balls attached to the top that went up his entire back and 3 feet above his head. This was done so that the actors that shared scenes with him would be able to have a reference point for where his eyes would be; the two red balls represented the placement of Ultron’s eyes. Elizabeth Olsen stated that this was actually distracting because Spader would be giving an intense performance and out of instinct she would look at him rather than the balls representing his eyes. Much to everyone’s amusement, whenever this happened, Aaron Taylor-Johnson would yell, “Red balls! Look at his balls, Lizzie!” at her in order to get her to look in the right direction.
There are a lot of apes and gorillas and cats in Hulk. I was using a lot
of that stuff in the first one. This one has that. Rage is one emotion.
It’s hard to give it much geography when it’s just rage all the time.
I’m finding other primal things in him this time that I wouldn’t have
thought to bring into it. The script also opens it up to that. He is
like another person. He’s an aspect of Banner that the volume is so
pumped up on. It’s very primal. It’s almost like the pre-consciousness
of Banner. It’s very base in its needs and I see there’s lust, there are
the essential parts of a person there. -Mark Ruffalo