The best retcon in the Marvel Cinematic Universe has to be putting Spider-Man into Captain Marvel being the first hero Nick Fury met, but the best one comes from Iron Man 2.

Following the success of Don Cheadle famously replaced Terrance Howard as Rhodey. The film hit theaters in May 2010 and was another hit for the studio, even if reviews weren't as kind this time around.

Related: Every MCU Movie Iron Man 2 Set Up

The biggest complaint that Iron Man 2 receives is how focused it is on universe building. Marvel needed to quickly pave the way for Wakanda in the final scene). Despite all of the planning, it is an unexpected connection that stands out above the rest: retconning Peter Parker into Iron Man 2.

The Kid In Iron Man 2 Is Peter Parker

Peter Parker In Iron Man 2

The climactic battle of Iron Man 2 takes place at Stark Expo on the night of Justin Hammer's presentation. Unbeknownst to him, Whiplash has spent his time reprograming Hammer's ripoffs the Iron Man suit to follow his every command and uses them to launch an attack on Iron Man once he crashes the presentation. This leads to these suits attacking Stark Expo and those that are in attendance. While trying to find a way to stop Whiplash, Iron Man must also take down all of his drones before they hurt any more civilians. In one of these instances, Iron Man swoops in and destroys a robot that is ready to kill a kid wearing an Iron Man mask. Tony blasts the bot and says, "Nice job kid," to the child he just saved. That kid was none other than Peter Parker.

This originally was just a theory that many fans had, but then Spider-Man: Far From Home later this year; but even if not, it's a very powerful idea.

How The Iron Man 2 Cameo Helps Spider-Man's MCU Arc

Spider-Man on top of a train Homecoming

Although this small retcon may not seem like much at first, it actually strengthens Peter's arc in the MCU. When we were first properly introduced to Tom Holland's version of Peter Parker in Captain America: Civil War, he is starstruck when Tony Stark appears in his apartment. Yes, Tony Stark is one of the biggest celebrities and heroes in the MCU, but this suddenly becomes a more personal moment for Peter given their previous encounter. He's not just properly meeting a hero of the world, he's meeting the man who saved his life all those years ago.

Related: The Biggest (And Best) Change The MCU Has Made To Spider-Man

It also further explains why Peter idolizes Tony Stark more than any other superhero; his chronologically first appearance instantly establishes that Peter is a giant Iron Man fan, wearing a toy mask of (presumably) his favorite superhero. This can even be taken a step further that Peter wants to be just like him even at a young age. Instead of running from the Hammer drone, Peter stands there and raises his arm to act as if he has all the power of Iron Man.

Page 2 of 2: How & Why Marvel Made The Spider-Man/Iron Man 2 Retcon

Spider-Man MCU Sony SR

That Was Never Meant To (And Couldn't) Be Be Spider-Man

As cool as the Spider-Man/Iron Man 2 cameo is, it could only ever be retconned years after the fact. When Marvel Studios was working on Iron Man 2, they did not have any access to Spider-Man. Sony purchased the film rights to the web-slinger and his full array of characters decades ago, and when Iron Man 2 was released in 2010, Sony was figuring out what would come next for Spider-Man on the big screen after Sam Raimi's The Amazing Spider-Man into the MCU, no such deal transpired.

Due to Sony still holding control of Spider-Man's film rights, Marvel could not legally use Spider-Man in any way at this time. That changed in 2015 with an unprecedented deal in 2015 that allowed Spider-Man to be shared by both studios; the Garfield series was ended and Holland entered as the MCU Peter Parker. It was only at this point he could be integrated into Captain America: Civil War and have a backstory worked into the previous movies. Bottom line, Kevin Feige and his team of producers may plan films, storylines, and character introductions years in advance, but this is not one of those instances.

Why Marvel Made The Spider-Man/Iron Man 2 Retcon

Tony Stark and Peter Parker walking side by side in Spider-Man Homecoming.

But legal logistics only explain the how, not the why: why exactly would Marvel Studios go out of the way to approve of a fan theory about a 2010 movie? It may simply just be because it is such an easy one to do. Plainly, it worked effortlessly. There's no exact age given to the child at Stark Expo, and even with the MCU's sometimes confusing timeline, it is easy to believe that the kid under the mask is a younger Peter Parker. Plus, this theory is one that may have been just too good for Marvel to take advantage of, especially as Marvel began to lean heavily on Spider-Man and Iron Man's relationship.

Related: The Key Difference Between Iron Man & Man of Steel (That Defined Their Universes)

Tony was there for Peter's first scene in Captain America: Civil War and has taken the young hero under his wing. The bond they share only grew in Spider-Man: Homecoming as Peter tried to prove to Tony that he's every bit of a hero as his longtime idol. And of course, them going on their intergalactic journey in Avengers: Infinity War further showed that this relationship has become much more than just a mentor and mentee. There is a father-son dynamic at play, felt when Tony's trying to keep Peter out of harm's way by trying to send him back to Earth, and in the heartbreaking goodbye they share as Peter is turned to dust. Iron Man was already part of Peter's life long before he gained superpowers of his own, but now there's just an extra layer of meaning thanks to this retcon.

Even though Marvel never planned on Iron Man 2 featuring Peter Parker's introduction, it was a brilliant choice to make.

MORE: Everything We Know About Iron Man's Role In Avengers: Endgame