The end-credits scene in Jon Favreau's "Iron Man" (2008) established a now-beloved tradition in the MCU universe, while making a promise to both comic book fans and everyone who loved the first true MCU movie that there would be much more to come from the tin-can-suited Tony Stark (Robert Downey Jr.). Yet instead of simply hinting that Stark would be back for a new adventure, it promised that the entire Avengers team from the comic books would assemble.
At the time, it was a pretty groundbreaking move. Up until that point, the movie world had never seen an epic, superhero team-up movie where heroes introduced in their own hugely successful movies would band together to fight as one.
