A climate scientist is infected with an energy-draining parasite.
Tropes in this episode include:
- Adaptational Heroism: Rudy Jones is still a villain like in the comics, but here he's re-imagined as a Well-Intentioned Extremist who considers humanity a threat to the planet.
- Adaptation Species Change: In the comics, the various versions of Parasite were all humans who received their powers from different kinds of phlebotinum. Here, Parasite is born when an actual alien parasite merges with a human.
- All Love Is Unrequited: When Alex kisses Maggie, Maggie gently lets her down. Alex quickly leaves the bar, blinking back tears.
- Apologetic Attacker: Kara feels sorry for Parasite and gives him a chance to stand down. Sadly, he doesn't take it.
- Artistic License – History: Scandinavia was not in its Bronze Age in 3000 BC, and even if it had been, Vikings weren't a thing until the Iron Age. It is being said by an environmental scientist in a dismissive manner, however.
- Artistic License – Physics: Plutonium-239 does not glow electric blue, but having Kara hold what looks like a steel donut wouldn't have been as visually impressive.
- Attack Reflector: Guardian's shield sends Parasite flying with the same amount of force it was struck by. Subsequent uses don't do this, suggesting it's a power-intensive feature.
- Attention Whore: Mon-El accuses Kara of not only being good for the sake of being good, but also for her ego.
- Body Horror:
- In a corner of the DEO, Jones hocks up the alien parasite, which crawls out his mouth, up his face, and into his ear.
- Kara's body after being drained by Parasite is also a pretty gruesome sight, with a focus on Facial Horror.
- Clark Kenting: Averted for James's hero identity, as he has a mask that covers his whole face and voice-changer as well. And his suit is even lead-lined, so his identity can't be discerned with x-ray vision.
- Cliffhanger: Mon-El is kidnapped by Cadmus.
- Coming-Out Story: Alex tells Kara hers—Maggie forcing her to confront her feelings has stirred up a lot of buried emotions and half-remembered attractions to other girls (though nothing she ever acted upon), especially her best friend from high school. Kara is surprised, but supportive.
- Composite Character: James Olsen is given the superhero alter ego of the Guardian, who in the comics is a completely different person.
- Did Not Get the Girl: Unfortunately for Alex, Maggie doesn't return those romantic feelings—or at least, doesn't feel it's a good idea to initiate what to her would be a rebound relationship with a woman still coming to terms with her sexuality. She tries to make this clear and let Alex down gently, but Alex takes it very hard.
- Drowning My Sorrows:
- Mon-El getting drunk after seeing an unconscious Kara definitely has some shades of this.
- Alex doesn't come in for work and downs several drinks of alcohol after getting rejected by Maggie.
- Energy Absorption: Parasite's powers.
- Fantastic Racism: Kara still isn't over her racial prejudice against Daxamites, which is shown when she is disappointed in Mon-El and almost lets a racial slur slip.
- Foreshadowing: M'gann is initially hesitant to donate blood to J'onn until Alex tells her it's the only way to save his life. After he wakes up, M'gann notices his left hand trembling and gets visibly worried.
- Gargle Blaster: Aldebaran rum. It's straight-up lethal to humans and strong enough to get a Kryptonian drunk with one shot.
- Going to Give It More Energy: Kara kills Jones by having him absorb plutonium-239, which overloads him until he explodes.
- Green-Skinned Space Babe: Mon-El is given a drink order by a blue alien at the bar.
- Idiot Ball: Even after seeing footage of Parasite draining a person by touching them, Kara and J'onn still opt to use their fists, despite both possessing ranged powers such as telepathy or heat vision. They pay in full for their tactical incompetence when he steals their powers out from under them.
- Jerkass Has a Point: Mon-El is right in that he has no obligation to protect the world and he needs money.
- Locked Out of the Loop: Kara doesn't know that James is Guardian because his armour is lined with lead so her powers can't see through it.
- Luckily, My Shield Will Protect Me: Guardian fends off the mutated Jones thanks to Winn's body armour equipped with a foldable shield.
- Mythology Gag:
- Rudy Jones says that the human race is sucking the life out of the planet "like parasites"; Parasite is his comic-book identity.
- It's not the first time that M'Gann has given someone a life-saving blood transfusion.
- At the end of the fight with Parasite, Supergirl asks Guardian who he is. His answer? "A friend."
- Mon-El catches a car the way Superman was first depicted on the cover of Action Comics #1.
- Nested Mouths: The monster that Jones turns into has these.
- No Good Deed Goes Unpunished: After Mon-El finally tries to be better and help out a homeless man, said man turns out to be a Cadmus agent and shocks him unconscious to be taken away.
- No-Sell: Parasite shrugs off bullets and punches from super-powered beings without much difficulty.
- Powered Armor: Guardian's armor has proven to be durable enough and has Winn's tech support.
- Punch-Clock Villain: Mon-El isn't exactly sadistic or anything, he just sees beating up people as a legit way to earn money.
- Puppeteer Parasite: Rudy Jones seemingly doesn't really have control over anything the Parasite makes him do. It does choose its targets from among his anti-environmentalist enemies.
- Purple Is Powerful: Jones mutates into a purple monster after siphoning both Supergirl and Martian Manhunter at the same time.
- Shield Bash: James as Guardian uses his shield in a very effective and offensive way.
- Shout-Out:
- The episode starts out with a polar research station finding a canine that's infected with an alien parasite.
- Winn finds a video of an autopsy filmed in the research center on a Dr. Bailey's computer.
- When Parasite is sent knocking back from Guardian's Attack Reflector, Winn calls the creature "Grimace," and later a "purple people eater."
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Strawman Has a Point: Mon-El has every right to use his powers to make money, especially since he is stuck on an alien (to him) planet, and isn't obligated to go out and become a hero just because he has these powers. The only thing that's actually morally wrong is the job he had beating up people for money; there are any number of legal ways he could exploit his gift for profit. - Strawman Political: Dr. Jones is a Well-Intentioned Extremist targeting threats to environmental efforts, which means an advocate for a conference on climate-change denial is referred to as an amassing of evildoers and shown practicing a speech dismissing zealous liberals en route.
- Surprisingly Realistic Outcome:
- Mon-El goes out of his way to fight Jones in public without any way to obscure his identity. By the end of the episode, he is captured by Cadmus, who can easily identify him.
- Maggie turning down Alex, as Maggie just got out of a relationship, and Alex needs to figure herself out before jumping into one; Maggie knows that such pairings rarely turn out well. Also the reality that the person you have a crush on will not always reciprocate those feelings or will not immediately want to be in a relationship with you just because you like them.
- Unstable Genetic Code: Jones mutating into a giant, purple monster is attributed to him absorbing both Kryptonian and Martian DNA.
- Unsuspectingly Soused: Aldebaran rum is served to Kara and Mon-El as "a refreshing cocktail" for Kryptonians and Daxamites, but one shot is enough to get Kara completely and utterly wasted. Of course, she's not used to drinking anything strong enough to actually affect her.
- Vampiric Draining: Rudy Jones sucks the life force out of his coworkers after getting infected by the alien parasite.
- Well-Intentioned Extremist: Parasite wants to save the world from climatic destruction by eliminating humanity.
- What the Hell, Hero?:
- Winn gives one to James when he tries to rush him to finish up the suit.
- Kara gives one to Mon-El when she finds out he works as an enforcer, and for accusing her of being an Attention Whore.
- Alex gives another one to Mon-El when he refuses to help fight the parasite.
- Whole-Plot Reference: A team of researchers in the arctic encounter an alien life form that causes shape-changing and personality loss. Sounds like The Thing (1982).
- You Are Not Alone: How Kara tries to encourage Alex after her coming-out.
