- Alternate Aesop Interpretation: The interpretation that Sophie was right in her decision doesn't take her children's actions and reactions into account. Rebecca and Martin resolve to save their mother despite multiple chances to leave her to Diana; Rebecca's reaction to the suicide, which the film lingers on, is to scream and cry; and Martin stares into the middle distance as he is powerless to help. Additionally, the movie sets up a method of hurting Diana with the blacklight, which would've been harder but likely effective. Another way to take the ending is that, while those with depression might think it's heroic to kill themselves and remove the immediate problem rather than be a burden on their loved ones as they try to help, said loved ones would prefer to solve the problem the hard way and keep the afflicted alive.
- Alternate Character Interpretation:
- Stalker with a Crush: Combined with Psycho Lesbian. A potential explanation for the sheer lengths Diana goes through to keep Sophie all to herself. Their implied relationship in the mental hospital has shades of this, especially when you consider Diana's very specific hatred of both Sophie's husbands to the point that she murders them both and particularly Diana scratching the father out of little Rebecca's drawing and adding herself next to Sophie instead.
- Tragic Villain: A different interpretation of Diana is that what she told Sophie is true - she didn't actually die in that light experiment, but instead got shifted to a different plane of existence, and Sophie is now her only tie to the known world. When Sophie gets better, Diana loses that link, as evidenced by the Room Full of Crazy in the basement. Couple that with her having been kept confined in the basement for most of her childhood due to her light allergy.
- Author's Saving Throw: David Sandburg intended it to be just one standalone story with no thought toward sequels, but then started writing one entirely because of the Focus Group Ending inadvertently giving the message that depressed people should kill themselves.
- Complete Monster: Diana Walter, a sociopath since the day she was born, is sent to a mental institution after she played mind games with her father, ultimately causing him to kill himself. While there, she manipulates a depressed Sophie into becoming friends with her, and became physically abusive towards her, going as far as to break her legs when she heard that Sophie might be getting released. As a ghost, she latches herself onto Sophie, enslaving her in the process. Wanting Sophie to herself, she murders both of her husbands when they attempted to heal their wife's mind, and she stalks and terrorizes Sophies children Rebecca and Martin, eventually opting to kill them in utter defiance of Sophie's demands. When two police officers are alerted on a potential break in, they go to investigate; Diana savagely murders both officers, and attempts to kill Rebecca in front of Sophie. Self-serving and hostile, Diana sought complete control over Sophie's body, and would murder anyone who came in her way.
- Ensemble Dark Horse: Bret is the best character in the whole goddamn movie. What could have been the typical dumbass horror movie boyfriend who dies just to add drama was instead a likeable and resourceful young man who believes Rebecca when she explains the supernatural encounters instead of just blowing it off. The scene where he uses his car lights to ward off Diana has reportedly caused several audiences to start cheering. Even before that moment he was genuinely supportive of Rebecca and was the one pushing for a Relationship Upgrade, when it's typically the other way around in movies. Also helps that Sandberg himself said Bret was his favorite character as well.
- Fanon: Fans of the film and original short tend to theorize that Escher is the character of the 2013 short since we don't see her again. Considering that most (if not all) of Sandberg's shorts have Lotta be The Chew Toy of them, it wouldn't be surprising.
- Hilarious in Hindsight: Diana is played by professional stunt Alicia Vela Bailey. One year after this movie, she'll be the stunt for another character with the same name. Both films would even end up tied together when SHAZAM! (2019) featured a cameo of Mrs. Glover now working as a foster care counselor.
- Paranoia Fuel: Let's face it. After you watch this movie, you probably don't want to stay in dark places for too long.
- The Producer Thinks of Everything: In the climax, the muzzle flash from the officer's gun means that Diana is effectively Immune to Bullets.
- Unfortunate Implications: If you want to take the interpretation of Sophie's depression manifesting into the ghostly Diana then the ending where she kills herself to get rid of Diana, gives off the unintentional message that if you suffer from depression and you're hurting your family, you should just kill yourself, because they'll be better off without you. This hasn't gone unnoticed. David Sandberg has revealed that this is actually a Focus Group Ending, as originally her suicide didn't actually help, which audiences complained made it feel pointless. He actually suffers from depression himself, and has lived through a friend committing suicide, and was horrified to realize how people were taking the revised ending.
YMMV / Lights Out (2016)