Julia is a character developed by Sesame Street to broach the subject of autism. The muppet is scheduled to be introduced on April 10, 2017.

The TV show 60 minutes featured a segment on Julia, March 19, 2017.
Originally Posted by 60 minutes segment on Julia
But how to portray autism?

Christine Ferraro: It’s tricky because autism is not one thing, because it is different for every single person who has autism. There is an expression that goes, “If you’ve met one person with autism, you’ve met one person with autism.”

“Sesame Street” has always based its characters and content on extensive research. They regularly bring in educators and child psychologists. In the case of Julia, they also worked with autism organizations to decide which characteristics she should have and how best to normalize autism for all children.
NPR article - Julia, A Muppet With Autism, Joins The Cast Of Sesame Street

Sesame Street dedicated site for autism here.