I'm kinda confused I hear this a lot, but I don't understand what a flat look is? Please can anyone explain this to me?
Thank you

that isn't vibrant, happy, healthy looking. A drawn look, down, gloomy, etc.

My sister has severe autism but she always is smiling and laughing, we hear her laughing at night a lot and when she hears a song she likes or when one of her favorite movies comes on she smiles and dances to the songs. The other day she actually was crying at a part on the Lion King 2 when the 2 lions weren't allowed to see each other and a song came on about how they loved each other.
I've never seen this in any other autistic child and my thought about what the flat look was is right I just wasn't sure because my sister always shows her emotions happy, sad, angry and other kids that were in her classes that I've seen were a lot quieter than her, and didn't express their emotions through facial expressions like you said.
It's interesting, I just don't understand why my sister shows it through her face and other autistic children can't.

The Autism Spectrum is so-called because there are many stripes/flavors/presentations of individuals on that spectrum.

Flat affect was pretty well described. Basically a blah feeling inside that becomes expressed in facial expression, tone of voice, choice of dress, unenthusiastic behavior. In some of our people it can be a symptom of depression; in others, it's just there. I've known several kids at the higher end of the spectrum w/flat affect, but then I've known more kids on the higher end than those severely disabled by Autism.

But not everyone on the spectrum experiences flat affect -- and not everyone w/flat affect issues has them necessarily 100% of the time.

Best wishes.