The Russo brothers know how to whip up a storm of hype by doing very little on social media. Back before Infinity War came out they posted a couple of cryptic tweet images and the world went absolutely cuckoo over them, trying to decipher what they showed. In the end, it didn't really matter (can anyone even remember what they were of from the final film?) - what mattered was the encouragement to talk about the film.
And the same thing has now happened with their latest tease: a loaded image featuring Joe Russo (presumably because Anthony was wiped out when Thanos snapped - very clever) on an abandoned set and the caption "look hard."
Naturally, the response was as furiously excited as it was inevitable (though lots of it devolved into silliness, because this is 2018 and Twitter is a strange old place to spend your time) with fans flocking to decipher exactly what the image meant.
Is the ladder supposed to be an A? Is that an E? Is Joe Russo pretending to be a d? Could it really spell Falafel? No, probably not on that last front, but that's genuinely the way the online conversation has gone about it.
But what if the Russos' tease to "look hard..." isn't actually just an invitation to READ what's in the image. What if there's something else in there that gives away a big plot hint and also a suggestion of what Avengers 4's title could be? What if the element on that set that doesn't appear to have been set up to draw attention consciously is the thing we're supposed to be looking at?
As Erik Mathews on Twitter pointed out, the strange machine in the left-hand corner of the shot is in fact from another Marvel movie. Or two to be precise. Crucially, it appears in Infinity War without any context, suggesting it was seeded in there on purpose so we could find it when we went back...
And even more interesting as Mathews points out, the scene that sees its appearance in Infinity War is called Avengers Assemble on the Chapters section of the blu-ray. Does that mean it was included as a deep tease for the title? If so, that's exceptional work.
As some other fans have pointed out, that "machine" also appears in Ant-Man And The Wasp and is in fact a Quantum Engine, which suggests that that WILL be the key to the film's alleged time travel plot. So maybe the Russos were simply giving that infomration away, rather than the title?