Matt Shiverdecker’s review published on Letterboxd :
Nacho Vigalondo's follow-up to Timecrimes begins with a premise that I think many of us can relate to. Julio (played by Julian Villagran, who won Best Actor at Fantastic Fest last fall for the role) wakes up in a strange apartment and finds himself struggling to remember the events of the previous night. He slowly begins to realize he is in the apartment of somebody he went home with after a long night of drinking. In his case, that would be Julia (Michelle Jenner), who is hurriedly cleaning up the apartment and hoping that he'll take off so that she can begin her day.
What happens next is certainly an interesting "what if" twist. Their phones aren't working. The cable is out. The radio is broadcasting a fuzzy state of emergency message about evacuations. When they look out the window, Julio and Julia see a massive flying saucer hovering over the city and everybody else in town appears to be long gone.
Extraterrestrial reminded me a bit of Monsters insofar as that was also a dialogue-heavy indie drama combined with genre film conventions that did not play out in the way most might expect. Vigalondo is unquestionably an imaginative storyteller and it's amusing to watch his characters try and figure out how to handle such an insane situation.
The pacing is on the slow side and the film may have too much romance and not enough sci-fi action for some, but its simple charms won me over.