Following a mass prison breakout, Earth's mightiest heroes unite to form the Avengers, a team comprising Iron Man, Captain America, Thor, the Hulk, Ant-Man, Wasp, Black Panther, and Hawkeye.

It is ultimately revealed that Loki orchestrated the breakout and had the Enchantress form the Masters of Evil to distract the Avengers so that he can conquer Earth as well as the nine realms, including Asgard.

The team is joined by Ms. Marvel and the Vision as they face new enemies including Doctor Doom, Thunderbolt Ross, and the Red Skull, as well as alien threats such as the Skrulls, the Kree, and Galactus.

Numerous other Marvel Comics characters make guest appearances, such as Spider-Man, Wolverine, Ant-Man (Scott Lang), the Heroes for Hire, the Guardians of the Galaxy, Quake, Beta Ray Bill, Falcon, and Winter Soldier.

[10] Various characters were considered to appear in the series, including Nova,[25][26] Silver Surfer,[27] Sentry,[28][29] Hercules, Morgan le Fay, Taskmaster, Scarlet Witch, Quicksilver, and Doctor Strange, but were cut.

[37][38][39][40][41][42] In September 2020, for the 10-year anniversary of the series' premiere, Christopher Yost revealed further unrealized plans for characters, including Tigra, Namor, the Defenders, Nightmare, Magneto, the Brotherhood of Mutants, Modred the Mystic, Kulan Gath, the High Evolutionary, Chthon, Juggernaut, and the Brood.

He noted the depiction of positive messages and role models, saying that while the villains sometimes appear to gain the upper hand, the Avengers ultimately prevail, showcasing the heroes' bravery in their ongoing mission to protect the world from powerful supervillains.

He highlighted its faithfulness to the comics, its fun and ambitious nature, and its successful blend of large storylines and a vast array of Marvel characters.

Zalben stated that the series works well for both kids and adults, and not only considered it the best Avengers cartoon, but possibly one of the best Marvel animated shows of all time.

They praised the show for its well-constructed team dynamic, creating a core cast that felt both familiar and fresh, complementing the live-action Marvel properties at the time.

Dornbush and Rivera noted that there was still much to appreciate in the show's 52 episodes, making it a worthwhile revisit, especially during the long waits between live-action Avengers films.

He highlighted how the show adapted popular storylines, such as the "Avengers: Breakout" arc by Brian Michael Bendis in the first season, and an overarching plot involving Loki as the main villain.

Doran described the series as possibly the purest Avengers cartoon, filled with heroes working together, over-the-top villainous threats, and big action.

He also appreciated the overall sense of happiness in the show, adding that its catchy theme song was unforgettable, often lingering in viewers' minds until the next episode began.

Christopher Yost returned as the main writer, with Adam Dekraker serving as the comic's creative team, while Nuno Plati provided artwork.