In the scene where the man is looking at the pictures on the refrigerator, in the glass cabinet next to him you can spot a reference to the Zombies mode in the Call of Duty video games. There are the original four Perk-A-Cola bottles; Juggernog, Sleight of Hand, Double Tap Root Beer, and Revive Soda, as well as another bottle that says Zombie Repellant. This is the second time Travis Darkow has hidden a reference to Call of Duty Zombies in his films, the first being a sign that read "Ascend From Darkness" in his film Goodbye Tomorrow (2019).
The owl, the deer, the seagulls and the swallows listed in the credits is an ongoing joke in a number of Travis Darkow's other films, where an animal or insect gets an "and introducing" credit. The names given to the animals are; Winston the Owl, Lucas the Deer, Wyatt and Jermaine the Seagulls, and Caroline and George the Swallows.
There is a short scene after the credits of Travis Darkow's earlier film Goodbye Tomorrow (2019) that shows the doctor standing at the end of the bridge where Subject 17 was last seen running in the final scene of the film, and next to the doctor is another clone, presumably Subject 18. The doctor speaks the word Onus, causing the clone to pursue Subject 17. The word Onus is defined as: A difficult or disagreeable obligation, task, or burden. This is also one of the command words used in the SERVILE screenplay which takes place in the same world as this film, which causes the clone to obey the doctor.
The word spoken to Subject 18 that makes him kill Subject 17 is Onus. The word Onus is defined as: A difficult or disagreeable obligation, task, or burden. This is also one of the command words used in the SERVILE screenplay which takes place in the same world as this film, which causes the clone to obey the doctor. When Subject 17 says "I'm so sorry, I tried, I really did" to which Subject 18 replies, "I know, burden of proof." This is another definition of the word Onus, and him telling the other version of himself that he understands that he's being controlled, and has no choice, because Subject 17 was once in the same situation in Goodbye Tomorrow (2019).
This film takes place after the events of Travis Darkow's earlier film Goodbye Tomorrow (2019), where clones of a man are sent through horrific simulations in order to test viability for mind control experiments, all for a shadowy organization who answer to an inter-dimensional entity known as the Dissimulator. All through Goodbye Tomorrow (2019) you follow the 16th clone of a man being experimented on, and at the end of the film, he dies and Subject 17 is awoken, but sees his own dead body, which causes a flood of memories that allow him to break free from the mind control drug and escape. Subject 18 is then awoken and sent to track down and terminate Subject 17. So throughout Litmus (2021) We follow Subject 19 who has just awoken, and who is being guided by Subject 17 to try to get him to wake up and realize what's being done to all of the clones of himself, as he tries to lead him through the simulations and get him out; all while being pursued by Subject 18, who is being controlled by this organization through mind control, but is still aware that he's being forced to hunt himself down.
Travis Darkow: [Shot of animal or insect] The bee symbol painted on the briefcase; as well as the owl, the deer, the seagulls and the swallows - Darkow often puts a small shot of an animal or insect into his films, and though they are cryptic, they all have a very specific meaning and purpose, though he rarely elaborates on them.