History Recap / Supergirl2015S2E8Medusa

* BigDamnHeroes: Subverted during Henshaw's fight with Supergirl. The breach appears, making the viewer think Barry is about to emerge and lend a hand (right after Henshaw [[TemptingFate Tempts Fate]] by saying, "No one is coming to save you"), only for it to close suddenly. Still, it distracts him long enough for Supergirl to regain her footing. Barry instead shows up at the end, after the main conflict with Cadmus is resolved.
** Mon-El gets a nod, since as others are running out of the bar, he is running back in to try to help. Granted, he has partial immunity due to his Daxamite physiology (partially Kryptonian), he had no way of knowing that at the time.

** Maggie admits to Alex that she has feelings for her after she almost died, and they kiss.
** Mon-El kisses Kara when he is dying from the virus, but claims to not remember kissing her after he is cured.

** Cisco is also seemingly still bitter about Barry indirectly causing the death of his brother (which he found out in the episode "[[Recap/TheFlash2014S3E7KillerFrost Killer Frost]]" that aired before this one), as [[FriendshipDenial he is quick to correct Barry when he calls him his]] [[FriendshipDenial ''friend'']].

** At the climax of the episode he also hands one to J'onn -- before the latter turns into a White Martian and gives it back to him (only being stopped by a sucker attack).

* FakeDefector: After being told that Lillian is the head of Cadmus, Lena calls her up and joins the cause, offering the isotope necessary to stabilize the Medusa virus. Turns out, she gave her the wrong isotope, rendering the virus inert, and called the police to arrest Lillian.

* FinalSolution: What Cadmus intends to do with the Medusa virus, killing all extraterrestrial life. You'd think they'd live over a wider area than a single city, but there wouldn't be anything to stop her from repeating the process elsewhere.
* FunnyBackgroundEvent: After Kara takes Alex's beer away before the Thanksgiving dinner and puts it in the freezer, Kara converses with Eliza. While Kara and Eliza are talking, Alex walks to the freezer, takes out a bottle of whiskey that was sitting next to the beer, and sneakily runs it back to the table.

* IfYoureSoEvilEatThisKitten: To prove her loyalty to Cadmus, Lillian tells Lena that she needs to launch the missile to wipe out aliens on Earth.

* MythologyGag: J'onzz's green "White Martian" form resembles his Franchise/DCAnimatedUniverse incarnation's true form.
* NeverTrustATrailer: The ads for the Arrowverse's big crossover event all claimed this episode was part of it, despite Marc Guggenheim being completely open before the season even started that it wouldn't be connected beyond Kara heading to Earth-1 at the end. In the final episode the only direct reference to the crossover are the momentary appearances of Barry and Cisco's breach, a less-than-a-minute-long sequence at the end where Barry and Cisco finally appear, and, thematically, this episode has similarities to the finale of the crossover as both involve human distrust of aliens and a bioweapon that targets a specific group for extermination.

* NotSoDifferentRemark: After finding out about her father creating Medusa (and the revelations about her mother a season earlier), all [[WellIntentionedExtremist for the supposed good of their race]], Kara starts seeing a few too many similarities between her parents and Lex and Lillian Luthor.
* OhCrap: Henshaw walks and talks like a real badass, but when J'onn morphs into a White Martian he simply stares in pure terror.

* MythologyGag: J'onzz's green "White Martian" form resembles his Franchise/{{DCAU}} incarnation's true form.

--->'''Cisco:''' "Friend" is a strong term; we work together.

* NotSoDifferent: After finding out about her father creating Medusa (and the revelations about her mother a season earlier), all [[WellIntentionedExtremist for the supposed good of their race]], Kara starts seeing a few too many similarities between her parents and Lex and Lillian Luthor.

* [[The Bus Came Back]]: Lena returns, having not been seen since the 5th episode.

** Cisco is also seemingly still bitter about Barry indirectly causing the death of his brother (which he found out in the episode "[[Recap/TheFlash2014S3E7KillerFrost Killer Frost]]" that aired before this one), as he is quick to correct Barry when he calls him his ''friend''.

** Maggie admits to Alex that she has feelings for her after she almost died and they kiss.

* BigDamnHeroes: Subverted during Henshaw's fight with Supergirl. The breach appears, making the viewer think Barry is about to emerge and lend a hand (right after Henshaw [[TemptingFate Tempts Fate]] by saying, "No one is coming to save you"), only for it to close suddenly. Still, it distracts him long enough for Supergirl to regain her footing. Barry instead shows up at the end, after the main conflict with Cadmus is resolved.

* ComingOutStory: The third episode in a row dealing with Alex coming out to someone. Alex through the first half of the episode is trying to build up the nerve to tell her mother that she is gay, only for it to be revealed that Eliza pretty much figured it out by the way her daughter was acting and their conversations about Maggie, and she reassures her daughter that she is okay with it.

** At the climax of the episode he also hands one to J'onn--before the latter turns into a White Martian and gives it back to him (only being stopped by a sucker attack).

* FunnyBackgroundEvent: After Kara takes Alex's beer away before the Thanksgiving dinner and puts it in the freezer, Kara converses with Eliza. While Kara and Eliza are talking, Alex walks to the freezer, takes out a bottle of whiskey, and sneakily runs with it back to the table.

* WhamEpisode: [[BigBad Lillian]] is finally arrested (although [[TheDragon Hank]] [[VillainExitStageLeft escapes]]) and Cadmus is seemingly defeated for now as a result. Also, some aliens want Mon-El, and they'll find him no matter how long they have to look.

!!Tropes in this episode:

* AlienAmongUs: Poor Mon-El tries very hard to get into the holiday spirit, wishing everyone a "Jolly Thanksgiving" and handing Kara a pillowcase loaded with fluff.

* BigDamnHeroes: Subverted during Henshaw's fight with Supergirl. The breach appears, making the viewer think Barry is about to emerge and lend a hand, only for it to close suddenly. Still, it distracts him long enough for Supergirl to regain her footing. Barry instead shows up at the end, after the main conflict with Cadmus is resolved.
* {{Bookends}}: To the finale chapter of the crossover as both episodes deal with a bioweapon that targets a specific group - aliens in the case of Medusa and metahumans in the case of the Dominators' weapon.
* BrokenPedestal: Kara grew up thinking her father worked saving lives, not harming people. His avatar clarifies, "''[[WhatMeasureIsANonHuman Kryptonian]]'' [[FantasticRacism lives]]."

* ComingOutStory: The third episode in a row dealing with Alex coming out to someone. Alex throughout the episode is trying to build up the nerve to tell her mother that she is gay, only for it to be revealed that Eliza pretty much figured it out by the way her daughter was acting and their conversations about Maggie and she reassures her daughter that she is okay with it.

** The aliens searching for Mon-El have tracked him down as far as the Well of Stars before losing the trail. Kara had [[Recap/Supergirl2015S2E1TheAdventuresOfSupergirl previously speculated]] that Mon-El's stay in the Well, where time doesn't pass, was the reason why he hadn't aged since Krypton's destruction.
** Winn says that a wormhole opening above the table was only slightly less intense than what happened [[Recap/Supergirl2015S1E5Livewire last Thanksgiving.]]
** Cisco is also seemingly still bitter about Barry indirectly causing the death of his brother (which he found out in the episode [[Recap/TheFlash2014S3E7KillerFrost Killer Frost]] that aired before this one), as he is quick to correct Barry when he calls him his ''friend''.

** He also makes good work of Kara later, though [[CurbStompCushion she get's a few good hits before.]]
** At the climax of the episode he also hands one to J'onn....before the latter turns into a White Martian and gives it back to him (only being stopped by a sucker attack).

'''Hooded Alien:''' Find it. I do not care how much space we must cross, how many lives we lose, or how many suns we burn. Mon-El of Daxam WILL BE FOUND.

* HeelFaceRevolvingDoor: Played with. Lena performs the "Face-Heel" variant as she appears to turn bad in order to trick her mother. Given, however, that she is a Luthor her true motivations are still not completely clear.
* IAmAMonster: J'onn admits this to Hank before transforming into a green version of the physiology of a White Martian to beat him up bare handed. Doubles as a PreAsskickingOneLiner.

* InternalReveal: {{Defied|Trope}} by Alex who doesn't want her own ComingOutStory at Thanksgiving to be ruined by James and Winn telling Kara about Guardian.

** In a meta example for Flash fans, Cisco's line about him and Barry not being friends brings up an unpopular plot development from that show.
* KryptoniteFactor: The Medusa Virus is designed to be a literally universal weakness for pretty much any non-Kryptonian species; the only reason it doesn't affect humans is because of Cadmus' modifications.

* TheMultiverse: While its inhabitants still think they are on the "one Earth," this world has been officially numbered Earth-38, in the Series/{{Arrowverse}} multiverse.
** In the final episode of the "Invasion!" crossover, Cisco gives Kara a device that can not only open a portal to Earth-1 but also will allow them to communicate back and forth.
* MythologyGag: J'onzz's green "white martian" form resembles his ''Franchise/{{DCAU}}'' incarnation's true form.

* NiceJobFixingItVillain: Lillian's smug assumption that Lena was as bad as she was allowed Lena to sabotage the virus, get Lillian arrested, prove that Kara's faith in her being a good guy was legitimate, and provide a means for Eliza to create an antiviral cure ''and'' a cure for J'onn.

* PretenderDiss: Kara tells Hank "You may be a cyborg, but you're no Superman."
* RedSkiesCrossover: "Part 1 of a four-night event" is how it was advertised; in practice, it's just a lead-in to the actual crossover spread across the other three shows. It doesn't even use the shared title. The episode is mostly focused on resolving the plot with Cadmus, and Barry only shows up with Cisco at the very end to recruit Kara. And coincidentally, there were red skies.

* TheMultiverse: While its inhabitants still think they are on the "one Earth," this world has been officially numbered Earth-38, in the Franchise/{{Arrowverse}} multiverse.