So y’know how there’ll be this story but there’s this one break from reality? The one thing that makes this world just a little different from the normal one? It’s pretty much the foundation of the story; the one pill that the audience has to swallow to make the whole story digestible.
If we can believe that ‘reality’ is really just a virtual construct and the real real world is a dystopian post-apocalyptic wasteland ruled by machines, The Matrix makes perfect sense. Since the world is virtual, running on walls and dodging bullets seems natural. Like Neo, we’ve gotta swallow that red pill and enter this world.
Or Harry Potter where there’s a secret society of wizards and witches and other magical people living right under our Muggle noses. If we can believe that, then the Ministry of Magic, Centaurs, and all the rest fit right in.
An audience’s willing suspension of disbelief is vital to a story. If they don’t buy it, they won’t invest. A lack of investment means they won’t care about it. And that’s terrible.
So how do audiences swallow this pill?
Well, a little bit of grounding helps a lot. Iron Man establishes Tony Stark as being a genius within the first fifteen-odd minutes of the film. With that in mind, it’s not hard to believe that he could build an Arc Reactor and a suit of powered armor in a cave with a box of scraps. It’s been established that he’s outrageously intelligent, so we buy it. When we see his garage/workshop we see that he has a couple of robot assistants with a limited amount of AI. Though this (and Jarvis, and his holographic workspace) is well beyond 2008 technology, we accept it because not only of how intelligent Tony is, but with the lack of focus he gives it. It’s simply there, it’s part of his world. Since it’s normal for him, it’s normal for us.
There is a limit, of course. In Iron Man 2 they filmed a scene where the Tony and Pepper’s jet flew in the upper atmosphere, where gravity no longer affected them. It’s no big deal for them. Ultimately, Jon Favreau and crew chose to cut the scene as it wound up being just too much. Introducing the idea of a jet essentially going into space would have been one piece of tech too much in a movie with AI and powered armor. It would have shattered the suspension of disbelief. There’s a limit to how much you can give the audience.
The Mass Effect games’ fantastic technology is all explained by the titular mass effect. It’s a fairly basic concept (currents applied to the mysterious Element Zero will either increase or decrease an object’s mass) that allows for faster than light travel, artificial gravity, and all that. Add some mysterious ancient technology and bam! Humanity joins the galactic community and gets caught up to speed with the other races.
It’s not another world (like Star Wars) or flung way in the future (Halo, Firefly, or Star Trek), but it’s believable because of the simple technological conceit they present. Furthermore, the idea of mass effects is not only exhaustively fleshed out in the game’s databank (encyclopedia) but is internally consistent. It has its limits: mass effect fields can do a lot but they aren’t magic. All this keeps it believable.
So we have movies with basic conceits: cursed treasure exists in Pirates of the Caribbean, the zombie apocalypse finally happened in Zombieland, Back to the Future asks you to believe that if you hit 88 miles per hour you will see some serious …stuff, in Up we believe a house can fly. It’s that doorway into the world.
Of course, like all things, it’s not set in stone. Sometimes you can just say the Earth was demolished for a hyperspace bypass and if you make it fun enough we’ll play along. Because sometimes the only rules you really need is the rule of of fun; so you can have Scott Pilgrim do battle with the psychic-powered vegan or Westley and Buttercup fight a Rodent of Unusual Size. These movies are fun, serious logic need not apply.
Unless, y'know, you break one of the rules you’ve already set up in your world. Then bam goes our suspension of disbelief.