And every time, there is a square-jawed hero, striking a pose in front of the Stars And Stripes, who single-handedly repels their otherworldly advances.
So in Attack The Block, a riotous action comedy from writer-director Joe Cornish, the aliens descend instead on an unsuspecting south London council estate.
The terrified residents of the capital should be no match for slavering beasties with luminous fangs... except the invaders don’t count on local knife-wielding hoodies with a serious attitude problem.
The wolf-like creatures soon realise that their devastating speed and strength are no match for the lads, whose merciless fighting instincts have been honed on their PlayStation and Xbox.
In space no one can hear you scream but in south London they can... they just choose to ignore you.
Trainee nurse Sam (Jodie Whittaker) is mugged on her way home by wayward lads Moses (John Boyega), Pest (Alex Esmail), Dennis (Franz Drameh), Jerome (Leeon Jones) and Biggz (Simon Howard).
The assault is thankfully cut short by a meteor shower and when the youths investigate, they come face to snout with a creature from another world.
“Are you trying to tell me it’s raining monkeys, bruv?” laughs one of the kids after they slay the snarling beastie and drag its lifeless, furry carcass to the top-floor drug den run by Hi-Hatz (Jumayn Hunter) and his lay-about door man, Ron (Nick Frost).
A second downpour of meteors heralds more creatures and the lads gleefully grab weapons and leap onto the bicycles and mopeds.
Attack The Block has the potential to be one of the surprise hits of the summer, boasting some energetic action sequences in and around the tower block as well as hilarious one-liners.
Cornish plays loose and fast with conventions of the genre and he doesn’t think twice about sacrificing some of his young protagonists to the creatures to underline the clear and present danger.
Transforming young people, who are demonised by society, into the unlikely saviours of the hour is a nice touch.
The young cast, mostly first-time performers, have an appealing rawness in front of the camera and Frost and Luke Treadaway, playing one of Ron’s posh punters, create a goofy double act.
For every generous splash of blood or edge-of-seat shock there is usually a belly laugh to dissipate the tension, whether it be one of the younger boys on the estate trying to create a rough and tough alter ego (“Me name’s not Gavin, it’s Mayhem!”) or one of the hoodies whipping out his mobile phone to message friends and whimpering, “This is too much madness to explain in one text!”
E.T. wanted to phone home but humans SMS.
:: SWEARING :: NO SEX :: VIOLENCE :: RATING: 7.5/10
Released: May 13 (UK & Ireland), 88 mins