Exactly. A lot of people don't realize when they meet someone with autism, because the person is performing a character in day-to-day life. If they perform well enough, you won't notice from brief or casual interaction. It's only when you get to know them that you see the cracks in the character when they apply it to situations that they haven't practiced for.
When performing in a play or show, they can just rehearse, and if they're skilled enough they can nail it. Try to get them to ad lib though, and they'll suck at it pretty bad if they don't have an appropriate canned response. Smart autists will try to anticipate a situation they might encounter and practice in front of a mirror to try to come up with something good to deal with it.
Chris only knows how to play a cartoon character, and because he's so isolated, nobody's trained him to even do that well.