In addition to a model of a Constitution-class ship, representing the Enterprise, Lt. Ortegas also has a model of a Walker-class ship in her quarters. The Walker was seen in the first season of Star Trek: Discovery (2017), represented by the USS Shenzhou.
One of the crewmen lost on the previous mission to Rigel 7 is identified as "C. Plummer." Veteran actor Christopher Plummer played General Chang in Star Trek VI: The Undiscovered Country (1991).
The painful condition of Tinnitus is mentioned prominently in this episode. William Shatner developed a severe and decades long case of this "ear ringing" during the filming of the TOS episode "Arena" as he was required to run through a series of simulated explosions as part of a Gorn attack on the Enterprise landing party.
This is the third episode where Dr. M'Benga and Lt. Noonien-Signh exchange a greeting that has them pointing a finger to the bottom of their eye and then moving it outward, however this time it is Lt. Noonien-Signh who starts the greeting.
Rigel VII is the planet in the first pilot of the original series where Pike encountered the giant warrior in the castle.