The sharp-tongued humor that became a trademark of Tony Stark was already present in the “Iron Man” comics, and the screenwriters of the characters’ MCU appearances evoked it diligently and brilliantly, but much of Stark’s snoring charm can also be attributed to Robert Downey Jr. self. In addition to often improvising lines, Downey spoke when he felt a line in the script was not up to standard. This was the case with Stark’s original quip after waking up from his unconscious state in the middle of the Battle of New York: “What’s next?”
According to Weekly entertainment, Downey pushed for the line to be changed to “something snappier” during filming, prompting writer-director Joss Whedon to come up with three pages of potential one-liners that Stark could blow out after regaining consciousness. They eventually went with “Tell me no one kissed me,” but the wealth of new material was such that they also included Tony’s suggestion that the team take a day off and grab shawarma: “I do not know what it is, but I will try it. “
Originally and until the film’s Hollywood premiere in April 2012, that was it – just a toss-up joke without payout. But after the production was packed, the creators of “The Avengers” created that a scene at the shawarma site would be a perfect fit for the vacant post-credits slot. So they brought the cast back on set the day after the premiere, covered Chris Evans’ beard with a prosthetic chin and shot the now famous code.