http://www.cbsnews.com/news/julia-first-sesame-street-muppet-with-autism/
“Her eyes had to be a certain way because she has to have an intense look, but she has to look friendly,” Krewson tells Stahl. “Her hair had to be made so that her bangs weren’t in her eyes and that her hair didn’t fall into her mouth. And she couldn’t have any adornments in her hair—no barrettes, no ribbons.”
Her clothes are equally intentional. Her purple dress is loose, without distracting bows, buttons, or ribbons. Even her eyes can change, depending on the scene; Krewson includes a half-closed version and a totally closed version so that if Julia gets upset and overwhelmed, she can close her eyes.
Occasionally two people are needed to operate one Muppet – one for the head and body, and one for the arms. When Julia flaps her arms, for example, a second puppeteer controls them.
But even though they’re not on camera, the puppeteers are still performing.
Like lots of kids on the autism spectrum, Julia has heightened sensitivity to noise, so when she hears sirens, they overwhelm her, triggering a meltdown.