• The episode title, “The Inner Fight” calls back to two previous titles, TNG’s “The Inner Light” and VOY’s “The Fight”.
• We’ve seen outpost scientists wearing the same jumpsuits as the Persioff IX researchers in “Mining the Mind’s Mines” and “Reflections”.
• T’Lyn comment’s that Mariner’s behaviour ”has grown increasing dangerous since [the] mission to Ferenginar” referencing travel guide updating duty the Lower Deckers were assigned in “Parth Ferengi’s Heart Place”.
• Ransom pulls up a display of four of the vessels we’ve seen attacked by the Mysterious Threat over the course of the season: Bynar, Orion, Romulan, and Ferengi. The only ship missing is the Klingon Bird of Prey, IKS Che’Ta’.
• Ransom specifies that all the attacks have been against non-Federation ships, which establishes that the Bynaus is not a Federation member world.
• Apparently someone is targeting ex-Starfleet officers, and there are four specific individuals the Starfleet is concerned about locating:
• Seven of Nine - Though she severed on the USS Voyager, Seven of Nine was technically never Starfleet; instead she was more akin to a civilian contractor. She will not actually become a Starfleet officer until season three of PIC, 20 years after this episode, more or less. Seven may have already joined the Fenris Rangers by this point.
• Beverly Crusher - At this point, Doctor Crusher has left Starfleet and is still pregnant with, or has given birth to her son with Captain Picard, Not David Marcus.
• Thomas Riker - Will Riker’s transporter duplicate. Last seen in “Defiant” leading a team of Maquis. He turned himself over to the Cardassians to serve in a labour camp; Kira gave him her word they would get him out, and he was never mentioned on DS9 again.
• Nick Locarno - The senior cadet in Nova Squadron, Nick was expelled from Starfleet Academy after getting one of his team members killed performing a dangerous and banned flight maneuver, and then getting the other members to lie about it, in “The First Duty”.
• Ransom summarizes the events of “The First Duty”.
• The USS Vancouver was seen in “Cupid’s Errant Arrow”.
• Mariner, Tendi, T’Lyn, and Boimler take the shuttlecraft Death Valley on their danger buoy girls trip, which is the shuttle Tendi arrived to the USS Cerritos on in “Second Contact”.
• Normally the Death Valley has the same NCC-77567 registry that all the Cerritos shuttles have, but in this episode we see that registry, along with NCC-70492, which is the registry of the Vancouver.
• Tendi comments that it looks as though someone tampered with the communication relays on the danger buoy, and then we see it through the viewscreen of the Che’Ta’. In “The Vulcan Hello”, the USS Shenzhou was investigating a communications relay that had been sabotaged by T’Kuvma’s followers.
• The Che’Ta’ appears to be under the command of G’reck, who was introduced in “wej Duj” as one of the Klingon lower deckers.
• In “Twovix” G’reck commented that Ma’ah “[would not] be captain much longer,” and his spear was the one floating in the fabricated wreckage of the Che’Ta’
• When we see the exterior of the Che’Ta’ is has a representation of the Kolvoord Starburst, as shown in “The First Duty”, painted on the port wing structure.
• Nick has the same image on his jacket when we see him later in the episode.
• On the planet Sherbal V, we see the commanding officers of various ships attacked by the Mysterious Threat throughout the season:
• Gem - Ferengi captain introduced in “Parth Ferengi’s Heart Place” - played by Eric Bauza, who a number of characters in PRO, LDS, and the “Very Short Treks”, including Ass Face, Screwhead, and the information broker in this episode
• Vreck - Romulan sub-commander introduced in “I Have No Bones Yet I Must Flee” - played by Paul F. Tompkins who is the voice of Doctor Migleemo
• Ma’ah - Klingon captain introduced in “wej Duj” - played by Jon Curry
• Cosmia - Orion captain introduced in “Something Borrowed, Something Green” - played by Kari Wahlgren voices a variety of LDS characters, such as the Anabaj from “Envoys”, and news anchor Sylvia Ront in “Grounded”
• Z’oto - Orion first officer introduced in “Something Borrowed, Something Green”
• The Ferengi first officer introduced in “Parth Ferengi’s Heart Place”
• The Romulan officer introduced in “I Have No Bones Yet I Must Flee”
• The Bynar co-captains introduced in “A Few Badgeys More”
• There is also a pair of Cardassians commanding officers; we did not see any Cardassian vessels attacked by the Mysterious Threat
• When Ma’ah steps in the trap set up by Gem and Vreck, we see that his blood is a bright pink, as Klingon blood has occasionally been depicted, such as in “Star Trek: The Undiscovered Country” and “Battle at the Binary Stars”.
• G’reck’s blood is also the same colour and Ma’ah bites him to death.
• ”Captain, did you know we have pockets?” Rutherford discovers that Starfleet uniforms are made from smart technology that accommodates the wearer’s needs, such as in “Ensign Ro” when Ro was able to unzip her uniform jacket in the front, despite the uniform clearly having its closure in the back.
• Cap’n Freeman, Rutherford, and Shaxs visit Mudds, a dive bar which shares it’s name with one Harcourt Fenton Mudd, introduced in “Mudd’s Women”.
• The doorman at Mudds is played by Paul Scheer, who voices chief engineer Billups.
• ”Jippers are half price for tripeds today.” In “The Escape Artist”, Mudd’s android duplicates were programmed to claim, ”If I had any money, I’d be sipping jippers on a beach somewhere.”
• ”The Klingons are up to something. Just like when they attacked us with the Pakleds.” Mariner references the events of “wej Duj” and she, Tendi, and Boimler learn that T’Lyn was present at that fight. T’Lyn also apparently learns that the Cerritos was Starfleet ship the VCF Sh’vhal was fighting alongside.
• ”Teach me how to tap-dance, Beverly Crusher.” We learned in “Data’s Day” that Doctor Crusher was once known as the Dancing Doctor, and she taught Data to dance in that same episode.
• Mariner explains to Ma’ah that she received a promotion she didn’t want, and that she tired to get demoted but her commander wouldn’t follow through, recalling events in “Twovix” and “I Have No Bones Yet I Must Flee”.
• ”Back at the Academy my dream was to be a captain.” In “Much Ado About Boimler” we learned that everyone in Mariner’s class thought she would be the first of them to make captain.
• We learn that Mariner was friends with Sito Jaxa, who was introduced in “The First Duty” and died in the TNG episode, “Lower Decks”. Mariner references both episodes explaining who Sito was to Ma’ah.
• We learned in “We’ll Always Have Tom Paris” that Mariner was stationed on Deep Space 9, but this is her first mention of having actually fought in the Dominion War.
• “Klingons do not hug!”
• Worf hugged an Edosian woman in “Justice”
• Worf hugged Alexander in “Reunion”
• Kor hugged Jadzia upon their reunion in “Blood Oath”
• Worf hugged Doctor Crusher in “The Bounty”
• Worf hugged Troi and Riker in “Surrender”
• Worf hugged Raffi in "The Last Generation"
• The information broker has had cosmetic surgery to resemble the puppet Balok used to appear intimidating in “The Corbomite Maneuver”
• Tendi is able to use her leverage as Mistress of the Winter Constellations to get Cosmia to listen to Mariner. We learned of Tendi’s title during the first girls trip in “We’ll Always Have Tom Paris”.
• Nick Locarno was behind the Mysterious Threat! The Nicksterious Threat!
• Nick is voiced by Robert Duncan McNiell, who played the character in “The First Duty”, as well as Steth and Janeway in “Vis à Vis”, and the Marseilles character featured in the EMH’s holonovel in “Author, Author”.
• The animated version of Nick Locarno looks similar to the animated version of Tom Paris, both there are some noticeable differences beyond the stubble and scar. Nick eyebrows angle up, where as Paris’ angle down, and Nick’s nose points down while Paris’ is slightly upturned.
I assume it was because you were tracking down instances of Klingons hugging?
It was a lot to scrub through every episode of Trek to find all the relevant instances, but I do feel like that’s the sort of accuracy people have come to expect.