Warning: contains one absolutely gargantuan spoiler for Avengers: Endgame, and it's right up the top here so if you don't turn around right this instant you're going to fall headlong into it.

The nature of heroism is something the Marvel Cinematic Universe has been picking at for a little over a decade now, but it turns out that the final word on it was given to an extremely unlikely character.

Avengers: Endgame director Joe Russo says that despite having specifically pitched Robert Downey Jr the idea of having Tony Stark sacrifice himself to sort out the universe before anyone else knew about it, the true moral centre of the film isn't even human.

It's that rat which wanders across the dashboard of Scott Lang's van and boops the button that spits him back out of the Quantum Realm.

"This is the case, the mouse saved the entire universe," Russo told Chinese site Youth Circle. "It is indeed a big coincidence, so Dr Strange has only seen this possibility in 14 million deductions. In the other millions of deductions, the mouse did not press the button, and the latter did not happen. In countless futures, there is only one future where the mouse is pressed [sic] and the world is saved."

You'll have to forgive a couple of slightly wobbly sentence constructions that make Joe Russo sound like a cave-dwelling mystic - the rough translation we've got also renames Endgame as, variously, 'Avengers 4', 'Join 4', 'Reunion 4' and 'Reunification 4', and rechristens Robert Downey Jr as "the little Robert Downey". There's also the tale of how Russo texted the little Robert Downey about how well the box office was going, and in return he, erm, "felt the excitement of Downey through SMS". Probably better to keep that stuff for Snapchat.

Actually, if you've got time, the whole interview's worth a read. There's no warm-up, no so-you-must-be-pleased-with-the-box-office softballs. It's just fan theories fired hard and fast at Russo's head.

The first two questions take quite aggressive issue with why Stark had to use the Infinity Gauntlet ("Why did you let Iron Man start the screaming moment at the last moment, instead of letting Stars [Captain Marvel?], Raytheon [Thor], Captain Captain and others who can withstand the power of gems come?") and the trajectory of Peggy Carter's love life ("Peggy Carter should be at least 40 years old in 1970 and should have been married. Then, which captain did the American captain return to and dance with his girl?"). Top stuff.