Avengers: Endgame could have been a very different movie, and in some ways a much darker one. Writers Christopher Markus and Stephen McFeely took the stage at San Diego Comic-Con to reveal some of their ideas during the various drafting phases that didn't make the cut, and some of them are downright wild.

Io9 reports that in one iteration, Thanos returned to 2023 with the decapitated head of Captain America circa 2014, in order to intimidate the Avengers. That particular dark turn will be explained in more detail in the commentary track on the home release.

Another cut scene included Rocket explaining the Quantum Realm to Jane Foster. The writers also considered having a reunion of sorts between Cap and Red Skull when he returned the stone, but that idea never got off the ground. One cut scene from Infinity War had Dr. Strange sending Thanos into his own mind to face a tribunal for his litany of crimes, but it slowed down the pace of the fight scene too much.

The writers declined to comment if the ending suggests there are two Captain Americas on Earth at the same time, but Markus did say he's "entertained" by the theory. The two also declined to speculate on where Gamora went, or if the MCU will further explore the multiverse. It seems like those decisions are being left up to other writers and Marvel story heads, respectively.

As for the film we did see in theaters, the "five years later" jump had a huge impact on all of the story decisions going forward. It gave them more space to explore complex character developments that would have developed over time, and it helped paper over a mistake they had made. "Smart Hulk" was originally set to emerge at the end of Infinity War. That moment was cut, but Endgame scenes with Smart Hulk had already been shot. The five-year jump gave space for Banner to plausibly reconcile with the Hulk persona.

Thor's story arc in Endgame was similarly in flux for a long time. The writers said that his story "sucked rocks" and wasn't character-focused. The eventual Thor story came out of an emergency all-hands meeting meant to get the character's trajectory back on-track.

Lots more is coming from Comic-Con this weekend, including plenty of Marvel events, so keep an eye out for more in the days to come.