Marvel Cinematic Universe: 10 Biggest Retcons Made By Marvel Studios

Rumour has it that Marvel Studios President Kevin Feige wasn't a fan of Marvel Television being given free rein to tell stories set in the MCU, hence why Agents of S.H.I.E.L.D. has always been treated like something of an unwanted child (by the time the series ended, it wasn't even really set in this shared world).

This could explain why Marvel Studios decided to get rid of S.H.I.E.L.D. in 2014's Captain America: The Winter Soldier by introducing HYDRA. While that villainous faction's existence could have been teased over a number of movies, it was all crammed into just the one, and that meant some familiar faces were outed as being loyal to the evil organisation.

Iron Man 2 character Senator Stern was revealed to be part of HYDRA, while Agent Sitwell (a loyal ally to Agent Coulson in the likes of Thor and The Avengers) was also serving them in secret.

That was unlikely the plan for them from the start, but it made them both considerably more interesting. Sure, they weren't big name characters, but that doesn't mean this wasn't a cool retcon.