20 Movies That Could've Been Horror Movies

The marketing for last year's black comedy Twinless leaned heavily on the comedy part of that equation, selling it as a wryly funny drama in which two young men mourning the loss of their respective twin brothers meet at a support group for "twinless twins."

But the marketing gave virtually no indication of the film's bold first-act twist, that protagonist Dennis (James Sweeney) was actually romantically involved with Roman's (Dylan O'Brien) late twin brother Rocky, and more to the point, accidentally caused Rocky's death by distracting him when he was walking in traffic.

And it gets even darker from there - we later learn that Dennis never even had a twin brother, ultimately fabricating one so he could get close to Roman.

While Twinless makes little attempt to downplay the creepiness of Dennis' actions, it's also fair to say that there's a whole other version of this movie that strips away the Sundance indie charm and unfolds as a purely nightmarish horror film about a uniquely unhinged stalker.