• The episode opens on L’ak’s funeral. Because he stabbed himself in “Mirrors”, and then intentionally overdosed on the drugs meant to cure him in “Erigah”.

• The…bridge(?) of the Breen dreadnought appears to have the floating wickets seen in this season’s credit sequence.

• We’ve seen Efrosians before in “Star Trek: The Voyage Home”, and “Star Trek: The Undiscovered Country”, but Hy’Rell is the first Efrosian woman we’ve been introduced to. She has more forehead ridges than the two previous Efrosians, though it's not clear if that's a redesign, or intended to be an example of sexual dimorphism.

• Burnham is very curt with Hy’Rell, cutting the archivist off multiple times as she explains the history of the Eternal Gallery and Archive. As all the lues leading to the Progenitor technology have thus far involved a lesson of some sort, no doubt the lesson being set up here is one about patience, and surely not just a bunch of faffing about before ultimately deciding the real lesson is the importance of self reflection.

• Cherenkov radiation was previously mentioned in “Choose to Live”.

    • In “Choose to Live”, Cherenkov radiation was said result from Tachyons interacting with an atmosphere, while here Tilly claims it is a byproduct of plasma activity.

    • In both cases, the Cherenkov radiation produced a blue glow.

• When Rhys claims the USS Discovery A won’t be able to cloak while in the pocket of the Badlands the Eternal Gallery occupies, Burnham claims that will also be true for the Breen, implying that the Breen’s cloaking device functions similarly to the Federation iteration of the technology.

• Hy’Rell is interested in having Book provide some information about one of the few remaining Kwejian artifacts stored at the Eternal Gallery. Kwejian was destroyed in “Kobayashi Maru”.

• Hy’Rell has the Eternal Gallery lower its shields so Burnham and Book can transport over. We’ve seen that in the 32nd century, transporters are not limited by shields, such as in the episodes “People of Earth” and “There is a Tide…”. Apparently the Eternal Gallery’s shields still block transporters.

    • The artifact is cutting from the a World Root, a system of tree roots that extended around the entirety of Kwejian before it’s destruction, first mentioned in “Kobayashi Maru”.

    • Hy’Rell only says the cutting came in to the possession of the Eternal Gallery, ”long ago,” without being any more specific. Kwejian was a pre-warp society when it was destroyed, though clearly some Kwejian, like Book, made it off world.

• The interior of the Eternal Gallery and Archive was filmed at the Thomas Fisher Rare Book Library at the University of Toronto.

    • The Eternal Gallery’s collection we see appears to be mostly hardbound, paper books. No doubt all the various alien methods of recording information are kept in other wings.

• Hy’Rell claims that the Eternal Gallery has an oubliette. In “Star Trek Nemesis” Riker the Reman Viceroy into a bottomless pit on the lowest deck of the USS Enterprise E.

• The script used in the book, “Labyrinths of the Mind” is the same as what was on the library card that led the Discovery A to the Eternal Gallery, confirming that is the Betazoid language, meaning the first time it was seen was in “Erigah”.

• Burnham’s consciousness is transported into an artificial reality.

    • Captain Picard experienced the end of the planet Kataan from the perspective of a member of that species in “The Inner Light”.

       • Doctor Culber says of the device affecting Burnham, ”It looks like some kind of nucleonic emitter,” and that he doesn’t want to risk severing the beam as it could be fatal. In “The Inner Light” it was a nucleonic beam from the Kataan probe which subjected Picard to his experience.

    • Captain Sisko, Jadzia Dax, Kira, and Doctor Bashir were transported into a Wadi game, Chula, in “Move Along Home”.

    • Rutherford was also trapped inside a Chula game in “In the Cradle of Vexilon”.

    • Harry Kim’s mind was trapped inside a shared consciousness ruled over by an evil clown in “The Thaw”.

• ”Jinaal would have let an itronok eat us,” Burnham recounts the test from “Jinaal”.

• The books accessed by Doctor Derex when she was an archivist include

    • “Comprehensive List of Talaxian Hairstyles”; a multi-volume set

    • “Huypirian Folk Tales”; several Huypirians have been seen severing as personal valets to various Nagi of the Ferengi Alliance

    • “Euclidean Geometry”; this is the first mention of a species called the Euclideans.

• ”Hysperians really know how to party, by the way.” Hesperia is a human colony of, as Rutherford puts it, “ren faire types.”

• ”Someone once told me never turn my back on a Breen.” Rayner shared the Romulan saying first spoken in “In Purgatory’s Shadow” in the previous episode, “Erigah”.

    • The Breen also have a saying; “Never turn your back on the wife of the Scion.”