To reduce fictional characters to real people, to apply the rules of human nature to them, cuts out their heart and soul and makes them as boring as, well, our daily lives would be if someone followed us around with a camera. What they do and say is more significant than it would be if you or I did it or said it. After all, we do and say things all the time that end up not meaning anything, but every detail in a creative work is important. Every word choice, the darkness and lightness of a scene, clothing and hairstyles, everything, is meaningful. Life is nothing like that.
Someone might say, "If they were real people the Michael and Brian friendship would be really destructive," and they might be correct. Several of the people on QAF would be insufferable to me if they were real people, for instance, Brian, because Brian hid many things about himself from the people in his life that are only visible to us as viewers. We see him when he's alone, which no one else does. We see his emotions when no one else does. If we were his actual friends or family in real life, we, like them, would not see those things. We wouldn't know Brian as we, the viewers, know him.
Do you see what I mean? We feel tender and protective of Brian based on things we wouldn't know about him if he were a real life human instead of a fictional character.
It's very inconsistent to analyze the show using information you could only ever have about a fictional character, but using concepts that only apply to real people. It might "feel" right, it might account for why we like and dislike certain characters on a TV show, but when you're actually analyzing the text itself, it just ends up being confusing.
I hope this somewhat cleared up what I meant by "extra-textual," and I apologize for the miscommunication! I truly did not know you're not a native speaker of English. I try to avoid doing that, but sometimes the fluency people have in slang, internet slang in particular, confuses me. :)