The Avengers: Earth's Mightiest Heroes

It was originally intended to make the season 2 finale a 3-part one where the Avengers would further explore Planet Hala (capital of the Kree Empire) after defeating the Supreme Intelligence, having a final confrontation against Galactus there instead of on Earth.

At the same time, that season finale would have originally made the New Avengers episode happen after Operation Galactic Storm, replacing the causes of their formation because the Avengers were on the other side of the universe and not because Kang took them out of time. Yellowjacket and Spider-Man would have been searching for Sentry (who was originally supposed to have been introduced in "Assault on 42" and have an episode focused on in it).

Josh Fine and a number of other creators of The Avengers: Earth's Mightiest Heroes were initially developing a series based on the Hulk.

The Spider-Man who appears in the series was originally supposed to be the same version of The Spectacular Spider-Man, with Josh Keaton reprising the role, but he was replaced with Drake Bell, who voiced the character in Ultimate Spider-Man.

Christopher Yost stated that it was originally planned to adapt the "Emperor Doom" comic arc (with the appearance of Wonder Man and the Scarlet Witch), which became the episode "Emperor Stark". He even sold copy ot the original script for such episode.

According to producer Josh Fine, due to executive changes during the second season, a planned multi-season story arc involving the Red Skull was compressed into the season's second half. Other ideas were to present the Winter Soldier in a more lethal, although less powerful way.