The fourth episode of Star Trek: Discovery’s second season is all about death, and perhaps, in some senses, rebirth.

The title of the episode, is “An Obol for Charon,” which references the Greek mythological god Charon and the specific way you bribe him. In order to get your soul taken to the right place in the underworld, you’re supposed to give Charon an “Obol” or payment. In ancient Greece, this sometimes meant putting money in the mouths of dead people. In this Star Trek episode it seems to reference the price everyone is paying for flirting with death, or in the case of the Spore Drive, traveling to the “underworld.”

Spoilers ahead for Star Trek: Discovery Season 2, Episode 4, “An Obol for Charon.”

Number One

This episode features the first appearance of Rebecca Romijn as “Number One.” The character holds the distinction of being the first first officer in Star Trek history, which makes her the number one Number One.

In The Original Series pilot episode “The Cage” (and the repurposed “Cage” footage in “The Menagerie”) Number One was played by Majel Barrett, the wife of Trek creator Gene Roddenberry. Both Number One and Barrett have a long history with Trek. 

Scotty loves the Enterprise really hard. But not yet!

Number One and Pike briefly talk about the current chief engineer of the Enterprise, who at this point is not Scotty. And yet, the future existence of Scotty is totally referenced when Pike asks Number One if the “Enterprise will ever have a chief engineer more in love” with the ship? The answer is yes, but not yet.

At this point, Scotty is clearly not the chief engineer of the Enterprise. But, that doesn’t mean he’s not out there in Starfleet already. Captain Lorca did a spot-on Scotty impression in Season 1 of Discovery, implying Scotty is an eccentric guy that people totally know about.

Rip out the holograms!

Pike tells Number One to make the communication system on the Enterprise retro on purpose. He seems convinced that the hologram system sucks and that screens are the only way to go. This retroactively “explains” why the tech on the OG Enterprise looks so dated compared to the slick tech of Discovery. Pike hates new things.

Number One’s data pad

The datapad Number One gives Pike also looks almost identical to the data pads from the original series.

Nhan is back from the Enterprise and she’s rocking a classic Trek mini skirt

Last seen in Season 2 premiere “Brother,” Nhan is back and serving on Discovery. Played by actress Rachael Ancheril, Nhan is a member of the Barzan species, first seen in The Next Generation episode “The Price.” The breathing device Nhan wears allows her to process Earth-like air that is normally toxic to her people. But, Nhan also rocks a mini skirt-style uniform, but this one is in the style of the Discovery uniforms.

Previously, when Nhan beamed aboard the Discovery, she was wearing red uniform with a black miniskirt, suggestive of the original series mini skirt uniforms, but also reminiscent of the non-gendered “skort” uniform worn by male and female crewmembers in the first season of The Next Generation. (Yeah, you forgot about the TNG skort didn’t you!)

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Extrapolating the sound of the sphere

Universal translator malfunction

The universal translator is a cornerstone of Star Trek tech and has been the go-to hand-waving catch-all solution as to why aliens are often speaking English in space. But, believe it or not, this is the first time we’ve seen what would happen if the the universal translator broke.

Tau Cetian language

Even after the universal translator is temporarily fixed, Detmer mentions that her control panel is still in “tau cetian.” This seems to reference a language indigenous to the Tau Ceti star system. In real life, there really is a Tau Ceti star system, and, in Star Trek, people have mentioned Tau Ceti a lot.

The planetary system is name-checked in the original series in “Whom Gods Destroy,” Star Trek II: The Wrath of Khan, the TNG episode “Conspiracy,” the Voyager  episode “Coda,” and the Enterprise episode “In a Mirror,Darkly.” Nobody ever goes to the Tau Ceti star system. They just talk about it a lot. So, we have no idea what the language Detmer was referring to would look like, nor what its people are like, either.

Dilithium mining is bad

When Stamets and Reno debate about the best way to propel a starship, Stamets says this: “Do you know how many planets were ruined by dilithium mining. How many wars fought over it?” This is a legit claim. Dilithium mining really sucks. In Star Trek VI: The Undiscovered Country, Bones and Kirk are sent to a Klingon prison where all they are supposed to do is mine dilithium.

In “Mirror, Mirror,” Kirk and the crew are trying to convince the Halkans to let them mine dilithium on their planet, which causes problems because the Halkans suggest Starfleet will only use the crystals to do terrible things. Relevantly, this episode is the first appearance of the Mirror Universe, which Discovery extensively visited in Season 1.

“Brightest Star” References

Throughout “An Obol for Charon” several references are made to the recently-aired Short Treks episode “The Brightest Star.” Saru mentions the concept of “the great balance,” and also the Ba’ul, the predator species that slaughters his people on Kaminar.

At the end of the episode, Saru asks Burham to cut off his ganglia with his sister’s knife, which she gave to him in “The Brightest Star.” Saru also talks a little about General Order One in reference to Kaminar. Basically, if one essential fact of his culture’s physiology is a lie perpetrated by an outside culture, then it seems like the Prime Directive might not apply anymore.

Virus as First Contact

Cortical implant

Speaking of Bones, Reno (Tig Notaro) seems to reference Dr. McCoy’s dilemma in Star Trek IV, when he argues that “drilling holes in his head isn’t the answer!” when the crew is trying to cure Chekov of head trauma. But, in this case, drilling a hole in Tilly’s head to install a cortical implant is the answer.

David Bowie

Tilly and Stamets briefly sing “Space Oddity,” the classic song by David Bowie. Obviously the line “I think I know which way my spaceship wants to go,” vaguely references all the spaceships in Star Trek, but it could be a direct reference to the Short Treks episode “Calypso” in which the Discovery does have a mind of its own.

Notably, David Bowie’s wife, Iman, appeared in Star Trek VI: The Undiscovered Country as a shapeshifter named Martia. These scenes took place in a dilithium mine, which Stamets and Reno debate about earlier in the episode. Plus, Undiscovered Country was directed by Nicholas Meyer who was the consulting producer on Discovery’s first season.

Spore Drive is actually harmful

In addition the sphere, Discovery is also dealing with another alien lifeform in this episode: the sentient fungus that has taken the form of Tilly’s jr. high school friend, May. Here, May accuses Stamets of being an “alien intruder” into her home in the mycelium network. This concept references numerous previous Star Trek episodes at the same time.

Finally, and perhaps most relevantly, the idea that the Spore Drive is harmful to an alien lifeform presents a huge case for why the technology doesn’t exist in the future of Star Trek. This kind of references the TNG episode “Force of Nature,” in which warp drive was instituted to be damaging the fabric of space. (Voyager kind of fixed that with new warp nacelles, but whatever.)

The big takeaway here is obvious. If the alien spore species that May belongs to is being terrorized by the Spore Drive, then Starfleet will totally shut it down, possibly by the end of this season.

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Ryan Britt is the author of the book Luke Skywalker Can’t Read and Other Geeky Truths ( Plume/Penguin Random House). You can find more of his work here.