While the Marvel Cinematic Universe (MCU) has been pretty good at shining a spotlight on its heroes from their first moments, there have been several characters whose importance has dramatically increased since they were first introduced. From the humble beginnings of Tony Stark’s Iron Man, the MCU timeline has grown to include entire multiverses packed with exciting characters.

And while everyone who has shown up in the MCU has some degree of importance, there are some characters who first appeared in a project in a supporting role, or occasionally even as a background character, only to develop into something much more significant over time.

8

Yelena Belova

Starting out strong, Yelena Belova made her MCU debut in Black Widow. In this film, she appears as the younger adoptive sister of Natasha Romanoff, with the two having spent years of their childhood together as part of an undercover Russian spy family.

While Natasha is central to the film, it was clear from the beginning that this movie was going to shift the focus onto a new hero, considering Nat died in Avengers: Endgame, and that film came out two years prior.

However, Yelena Belova has since become a more significant and connective part of the Multiverse Saga, both through moments like her meeting Hawkeye, and through her becoming a leader of the New Avengers. Yelena’s story is still in its early stages in the MCU, but it’s clear that she will have an important place in the future of its stories.

7

Rocket Raccoon

Another character who had a tragic upbringing – only to have his story arc take him all the way to the point of leading his own team – is none other than Rocket Raccoon. Rocket starts out as a very confrontational character, but by the time Guardians of the Galaxy Vol. 3 comes around, he’s become the emotional core of the team.

While Avengers: Endgame gives Rocket more screentime away from the Guardians due to the Snap, it’s the final movie in the trilogy that reveals Rocket’s full history as an experiment of the High Evolutionary, and his mistreatment at the hands of his “creator”. Naturally, this means Rocket’s story is especially focal in the third film’s story.

Rocket’s history shaped him into someone who struggled to trust and work with others, but he’s shown overcoming the traumas of his past throughout the 2023 movie. As such, it’s fitting that he becomes the leader of the Guardians of the Galaxy in the Guardians of the Galaxy Vol. 3 ending after Peter Quill decided to return to Earth.

6

Loki

On a different note, Loki actually started out as a villain in the MCU. Loki was first introduced in Thor, where he learns the truth of his heritage as an Ice Giant who was stolen by Odin, before turning on his adoptive father and brother.

Loki would go on to be the primary antagonist of The Avengers, where he killed Phil Coulson, and unleashed a devastating alien army on New York. This is the point where his story splits in the MCU, but on both multiversal paths, Loki steps up to become a hero.

In the Sacred Timeline, Loki goes on to repair his relationship with his brother in Thor: Ragnarok, before sacrificing himself to save Thor in Avengers: Infinity War. However, when the Avengers go back in time and mistakenly cause a variant Loki to escape, instead of being captured after the Battle of New York, this variant is captured by the TVA.

Outside of time and reality, this version of Loki becomes an even more remarkable hero, starring in his own series, Loki. By the end of Loki season 2, Loki becomes powerful enough to hold the strands of the multiverse together, becoming a guardian to all realities.

5

Bucky Barnes

In Captain America: The First Avenger, Steve Rogers has precious few friends, and he struggles to find where he belongs. However, his dear childhood friend, Bucky Barnes, has faith in Steve, and shows him kindness and love.

When Steve eventually receives the super soldier serum, he goes on to rescue Bucky and a whole unit of soldiers who were captured and trapped behind enemy lines.

Bucky is stunned to be saved by his formerly tiny friend, and the two embrace and become allies in a team known as the Howling Commandos. But before long, Bucky’s story seemingly ends when he falls to his death on a mission.

As it turns out, HYDRA captured Bucky and gave him a more experimental version of the super soldier serum, along with a robotic arm. This led to decades where he operated as the ᴅᴇᴀᴅly ᴀssᴀssin known as the Winter Soldier under the control of HYDRA.

However, when Steve met him after decades apart, he was able to coax Bucky away from HYDRA’s control, and recruit his friend to fight alongside him, leading to Barnes being an even more crucial part of the MCU’s story. Now, Bucky stands tall as a reformed ᴀssᴀssin, a former politician, and a hero in The New Avengers.

4

Sam Wilson

Another figure connected to Steve Rogers, Sam Wilson, was a dear friend that Steve met shortly after being unfrozen by SHIELD. The two bonded over their military history, and Sam stepped up to become an ally to Steve, known as the Falcon.

As the Falcon, Sam became an official Avenger, and he took part in fighting some of the biggest and baddest threats the team ever faced, including Thanos and his army. However, when Steve decided to retire and entrust his friend with his shield, Sam struggled to embrace becoming Captain America.

It took time, and Sam fought an uphill battle to be accepted by the world and himself, but eventually, he followed Steve’s wish, and he became the hero known as Captain America. Captain America: Brave New World took this one step further by teasing that Sam will be forming his own Avengers shortly, making him even more key.

3

Trevor Slattery

In Iron Man 3, it appeared as though Tony was finally going to confront the terrorist organization that had kidnapped him back in the first Iron Man movie. However, when Tony found the source of several terror attacks, he was stunned to find an inebriated British actor instead of the terrifying Mandarin.

As it turned out, Trevor Slattery was a classically trained actor, hired by another criminal, Aldrich Killian, to pretend to be the Mandarin. Trevor was being kept as a prisoner, and being used to create a distraction from the real mastermind, Killian, and his Extremis program.

However, Trevor’s impersonation of a legendary crime lord attracted the attention of the real Mandarin, which resulted in the character appearing again in Shang-Chi and the Legend of the Ten Rings. Here, he befriends a mystical creature that he calls Morris, with this friendship earning him a place in the magical realm of Ta Lo.

2

Wong

Diving into the world of the mystic arts, Wong appears in Doctor Strange, where he is a humble librarian in Kamar Taj who befriends a new but promising recruit named Stephen Strange. While Stephen appears to develop his powers at an extraordinary rate, Wong remains a constant, powerful force among the sorcerers.

When the Ancient One dies, Stephen progresses to become the new Sorcerer Supreme, but when Stephen fades from existence due to Thanos’ snap in Infinity War, Wong is advanced to the position of Sorcerer Supreme, due to Stephen technically being ᴅᴇᴀᴅ.

Even after Stephen returns following the events of Avengers: Endgame, Wong remains the Sorcerer Supreme, and leads the sorcerers at Kamar-Taj and around the world. Wong has since appeared in a variety of projects, once again serving as a major connector between the characters in the Multiverse Saga.

1

Madisynn King

Finally, there is Madisynn King. Madisynn first appeared in She-Hulk: Attorney at Law, where she is a background character. However, the way this character playfully engages with heroes like She-Hulk and Wong made her an immediate fan-favorite.

While She-Hulk remains the only mainline MCU project that she has appeared in so far, she appears to be living in Kamar-Taj, and could well return in a future MCU project. Beyond that, Madisynn has gone on to join the Marvel comics, officially cementing her as a part of these stories.

Though these characters all serve different roles, they’re all proof the MCU – and Marvel more broadly speaking – is not afraid to develop its characters and explore them in more detail as their stories progress. Ultimately, it’s great to see so many heroes and even minor characters step into larger MCU roles over time.