“These are things that just don’t happen.”
In Clark Gregg's own words, as told to BuzzFeed:
Clark Gregg as Agent Coulson in The Avengers
Via: Marvel Studios
"In the original script of Iron Man, I'm not even sure his name is Coulson — I think it was just 'Agent.' And then he had a name, and seven or eight lines. And then all of a sudden, there's a scene at the end where Pepper Potts and Tony Stark are saying 'Thank you, Agent Coulson.'"