The post-credits scene of The Avengers where the team is eating shawarma was added after the day after its Hollywood premier. The idea for this scene came about after Robert Downey, Jr. improved one of his lines. When he crashes to the ground after falling back through the portal, he was originally supposed to say “What’s next?” Downey felt the line could be more interesting, so he added the lines about going to get shawarma after they had defeated the Chitauri.
It was reported that shawarma sales received a boost shortly after the movie was released. Talk about free press!