The episode's title, as displayed on-screen, is written in Klingon script. This is the first time in all of Star Trek lore that an episode's title wasn't written in an Earth language.
"wej Duj" translates from Klingon as "three ships". "Che'Ta", translates to "Battle".
Boimler's rocket boots and "Go Climb a Rock" shirt are references to Star Trek V: The Final Frontier (1989). In that film, Captain Kirk wears a similar shirt, while Spock makes use of rocket boots.
Klingon blood is portrayed as bright pink, as it was in Star Trek VI: The Undiscovered Country (1991). However, throughout the rest of the franchise, Klingon blood has been red, just like humans. This is especially apparent in Star Trek: Deep Space Nine (1993), where Klingons were frequently wounded, and would often blood-let for ceremonies or to prove they were not Changelings. In Star Trek VI, the blood was bright pink to avoid an R-rating from the MPAA. It is unknown if the color of the blood here was to avoid similar censorship, or if it was simply a stylistic homage to Star Trek VI.
The ending scene of the lower decks of Borg cube 90182 is the first canonical indication that a traditional form of the Borg are active after Endgame (2001).