I've seen this episode! I never thought that a children's show would cover autism!
The way Carl behaves definitely includes some AS symptoms, like the monotone voice, obsessive interests (trains), making little eye contact, interpreting idioms/figures of speech literally, seeing things differently, sensory overload, particular eating/drinking habits (apple juice in a carton, not a bottle), one-way conversations about trains, drawing trains from memory (and noticing even the tiniest flaws like the windows being too big) and recalling information from George instead of greeting him.
Not all autistic people are like that, though. Carl is nothing like me. I really liked Brain's uncle's perception of the world. It made me think of living with autism differently, and now that's how I think of it. 