I want to try to develop some of the issues raised in comments about who actually exists in Bad Influence. Not so much because I think it matters who exists or not - but because the way film hints at the possibility, and then does not resolve it, raises points about information in films that I find fascinating.
So who is real? The film sets you up to wonder about Alex, especially - even raising the point explicitly. Pismo says the cops won't believe he exists - and that's the plot in the last third or so - how can Michael (and Pismo) prove that Alex exists, and that he did these things, not Michael? That's what happens in the last act - they chase down evidence that Alex exists - finally trapping him on the Manhattan Beach pier.... But what's interesting about the question is that the film doesn't resolve it. It maintains its ambiguity to the end. In fact, it probably raises more questions about what is real, without answering them. What about Pismo? He's even more ambiguous than Alex, if you think about it. We don't see anyone interact with him other than Michael and Alex. What's more - his function in the plot is as a kind of return of the repressed. He's more Michael's physical double than Alex (a fact the film plays with, from his introduction on.) He shows up at MIchael's door, asking for money, paranoid about an old drug conviction, or later, telling Alex he has "the fear." Which prompts Alex to ask Michael what he is afraid of, what he wants.
The question of what is real isn't all that important in itself. The symbolic links among the characters are obvious enough, and don't depend on their literal identity. What is interesting is how the film handles the possibility, and how it fits with other aspects of the film. How does the film handle it? By hinting at it - then raising it explicitly, and setting it up as the point of the story - then seeming to resolve it - but, rather pointedly, not resolving it. Most of the hints, in fact, are more about the symbolism than the reality of these characters. Alex doesn't really seem to be anything but a slumming gangster of some kind when he first appears. He plays tempter - plays Faust - though he also seems to be acting as Michael's id, or enabling Michael's id. The characters are linked - most clearly in Alex's first appearance in the bar. We see Michael at the bar drinking a beer - we see him in a fight, getting pushed around - then we see a closeup of a hand, breaking a beer bottle on the bar - then we see Alex. But that hand breaking the bottle - it's certainly edited to make us think for a second that's Michael... But even this is just a symbolic link - and symbolism isn't ontology.
Once Alex's existence is named as a problem, though, this manipulation of information becomes significant. You realize that the film has not shown us who beat Patterson, who killed Claire, you realize that no one has seen Alex except Michael (and Pismo and Claire, but one is as reclusive as Alex, and the other is dead). No one but Michael has talked to Alex on the phone. It is possible to put Michael and Alex in the same place for any of the important moments - and possible to rationalize Alex's presence (as Michael's imagination) at places where there seem to be witnesses (like the fiancee's party.) Episodes like the robberies are played ambiguously - we see Alex's face, but Michael wears a mask, and acts completely dissociated from the crimes, enough to make us question the point of view they represent. And everything that might count as evidence - the videotape, even the pictures we see at the beginning of the film, before Alex meets Michael - have disappeared, been destroyed, etc. Now: by naming the question (of Alex's existence) in the film, it sets you up to expect a resolution. The film never plays the story as if Alex didn't exist - everything is structured as if it were a mystery to be solved. And indeed - the ending of the film seems to solve it: Alex's confession is on tape - then he is shot....
And yet the film maintains its ambiguity. Alex's body doesn't come to the surface - no one actually watches the video footage. Michael walks off to talk to the police - but Pismo lags behind, and we don't actually see Michael meet the police. Nothing is resolved.
I think this is important. It does a couple things: one is, I think it links it to another branch of films, to art films - Antonioni and the like. It shares some of their aesthetic - the stark, urban landscapes, the blank white walls, the fascination with photography and video; and it shares their ambiguity, and interest in ambiguity. The unanswered questions of who killed who, or if anyone killed anyone, of Blowup or Terrorizer or a Michael Haneke film. I don't know how much connection there is to those films, probably some, though even without direct links, many of the ideas and images were in the air in 1990.
It's also important for foregrounding the question of evidence, in the film, and for film watchers. What constitutes proof that something is "real" in a fiction? Most of the time, we take it for granted - if the filmmakers put someone on screen and show something happening, we assume it is actually happening, within that fictional world. So why would we doubt that? Why would we ask if 2 characters are really the same person? Why would we ask if something was a figment of someone's imagination? and if the problem comes up - how do you decide, in the film, what is real and what is not?
How does this film suggest that Alex is not real? I'd say: 1) his introduction, that ambiguous cutting around the bottle; 2) by foregrounding the story templates, doppelganger stories, Faust stories; 3) by manipulating what we see and don't see - and then foregrounding the manipulation, so we notice that the film seems to have arbitrarily skipped something like Patterson's beating. 4) And finally - by making it an explicit problem for the plot - by having Pismo and Michael realize that they have no way of proving that Alex exists.... Or - how does the film prove that Claire (for instance) is "real"? Well - as I said in a comment: she's on tape - other people see her on tape. That's how we know Michael is real. We see people that we can't reduce to Michael's perception, and those people react to him: thus we know he "exists." And that evidence is missing for Alex - and for Pismo. Alex does not appear anywhere Michael is not, or if he does, Michael's independent existence can't be proved; there are no pictures of him (and he has no intention of letting anyone get any - they won't knock over a convenience store, it has cameras), no one hears his voice. Same with Pismo - again - only Michael and Alex see him, except at the club - which we could read as "really" Michael. (I think there's enough time to at least pretend Michael's trip to get the gun is not simultaneous.) No pictures of him, no one else hears him talk. And when there is a real chance of two of them being seen (as when they are trying to dispose of the body, or even at the end), Pismo conveniently disappears when people come along (or the film stops.)
But likewise - how would we prove that Michael and Alex are the same person? Well - the film could tell us, explicitly (as in Fight Club.) Or we could imagine a final scene - Michael telling the cops how Alex did what he did, showing them the tape - and we might see the tape, and see Michael confessing the crimes... Or we could see the cops coming to the end of the pier and see that what we thought was Michael was Pismo - and then see Michael's body in the water. There are undoubtedly more subtle ways of making the point - but of course, the film does none of them.
Anyway: that is all for now. By rooting through all this, I don't mean to say that the characters really are the same person, or that the question of whether they are or aren't is all that important. What I think is important is the fact that the film does not resolve the question - and that it does raise issues about knowledge and reality in film. The ways it relates those questions to technology - might be another essay...