There's no entertainment property today, perhaps ever, that's sparked as much continued interest and excitement as the Marvel Cinematic Universe.
Even the superhero franchise's "lesser" installments get the rumour mill running overtime as fans speculate, obsess, and agonise over what might happen, often before shooting has even started.
It can be a ton of fun poring over all the ridiculous-yet-enticing rumours and fan theories posted online about upcoming MCU films, even if the scuttlebutt often turns out to be nothing more than creative, wishful thinking on the part of overzealous fans.
While many absurd rumours are simply that - silly what-ifs that Kevin Feige would never dare sign off on - others have been genuinely, compellingly off-the-wall enough that fans lamented when they didn't end up happening.
These 10 rumours, from mind-melting fan service to genuinely thoughtful and intriguing plot twists, would've certainly gotten everyone talking and, in at least one case, absolutely broken the Internet.
We'll never know for sure if these rumours would've actually turned out better than what we got, but the fact that they were never realised remains a sore sticking point for many...
10. Alexander Pierce Is Red Skull - Captain America: The Winter Soldier
Marvel fans - and simply fans of good acting - were thrilled when Robert Redford was cast as prominent S.H.I.E.L.D. official Alexander Pierce in the second Captain America movie.
It wasn't long before Redford accidentally spoiled the fact that he was playing a secret villain, which in conjunction with one of the movie's action figure lines reportedly featuring the villain Red Skull, prompted the rumour that Pierce was actually Red Skull in disguise.
This was further bolstered by an alleged soundtrack leak which contained a track with the rather on-the-nose title, "Alexander Pierce is the Red Skull."
What Actually Happened
As incredible as it would've been to see Redford shed his skin to reveal a red noggin underneath - especially given Red Skull's history of infiltration in the comics - this was sadly 100% bunkum.
Pierce is indeed the movie's ultimate villain, but he's a strictly flesh-and-blood human bureaucrat who has been secretly working as Hydra's leader within S.H.I.E.L.D.
Redford knocked it out of the park regardless, and in fairness it's tough to imagine the legendary actor, almost 80 years of age at the time, wanting to bother with the extensive facial prosthetics required to play Red Skull.