Marvel Phase One feels like a long time ago, and if you haven't been back to revisit the stories from the dawn of the MCU, you're bound to have forgotten some odd plot details.
Whether it's from negligence or some subtle retconning, these are points that have been almost completely lost to history.
1. War Machine was someone else
Don Cheadle has a memorable supporting role as Iron Man's armoured comrade, War Machine, but it wasn't always so. Cast your mind back, and you might just remember that Terrence Howard originally played James Rhodes in the first film. Howard famously had a falling out with the folks at Marvel – and he never even got to wear the War Machine armour.
2. Tony Stark was an arms dealer
In Phase Three, Tony Stark has been portrayed as a mouthy but generally upstanding guy who wants to make the world a better place, even if he does make some huge mistakes along the way. No-one seems to mention anymore how he started out in 2008's Iron Man as a weapons manufacturer who sells guns and missiles to some very shady people.
One reason we probably forget this is that his father, Howard Stark, has been portrayed as a similarly irascible genius who dreams up some dangerous inventions but generally means well. Those two scamps have squeezed out the old, amoral version of Tony, and Marvel is probably happy for us to forget him.
3. Hulk had another one true love
People don't talk about Edward Norton's version of Bruce Banner very much, and that goes double for poor old Betty Ross, played by Liv Tyler back in 2008. Ever since Mark Ruffalo stepped into those big green shoes, she hasn't been mentioned once – not even by her dad, General Ross, when he reappeared in Captain America: Civil War.
4. Captain America was the creation of German science
Like the space race, the American Super Soldier experiment (aka Project Rebirth) would have been nothing without good old German ingenuity. In this case, Dr Abraham Erskine (Stanley Tucci) wasn't a Nazi, but he was forced to give the Red Skull superpowers before he fled to the US.
After Erskine's assassination, Project Rebirth stalled, and it took decades for them to reproduce even a flawed version of the Super Soldier Serum.
5. Hulk is a failed Super Soldier
Speaking of which, that failed attempt to recreate the serum led to Bruce Banner being turned into the Hulk (in The Incredible Hulk). Easily forgotten, as the traditional Hulk origin has Banner caught in an accidental gamma bomb explosion.
6. Loki is a frost giant
The events of Thor centre in part around Loki's realisation that he isn't Odin's biological son at all but a frost giant. This revelation came complete with blue skin and red eyes, but that transformation has never been repeated or mentioned again.
7. Multiple Hulk villains are still at large
The Incredible Hulk saw our green hero face off against another monstrous Super Soldier test subject, The Abomination, and also ended with a hint that the scientist Samuel Sterns would transform into another classic villain, The Leader.
The former has been alluded to in Agents of SHIELD and the latter was captured for SHIELD by Black Widow in a spin-off comic, but the organisation has gone to hell since then so who knows where they've got to.
8. Hawkeye was the first Avenger to encounter Thor
Before his less-than-inspiring role as Loki's meat puppet in Avengers, Hawkeye had a little-remembered cameo in Thor. They never actually come face to face, but he took aim at the thunder god before deciding to let him go. We count that as the first encounter between two (future) Avengers.
9. Thor was a natural blonde
When we first met Chris Hemsworth's thunder god in 2011's Thor, he was unsettlingly blonde to the point where his eyebrows were almost invisible. As the years have progressed, his facial hair got darker, and by the time Ragnarok came around in 2017 his hair was so dirty blonde as to be basically brown.
So either Marvel has retconned his Asgardian DNA or Thor was hitting the peroxide bottle when we weren't looking.
