Doctor Crusher’s serotonin isotope: In the Pretender 2nd season finale “Bloodlines,” a few episodes after “Crossover” takes place, Sydney begins running Angelo through a series of experimental treatments, hoping he can reverse his condition and bring back Timmy, Angelo’s former genius-self. Sydney tells Miss Parker that Jarod had developed the treatment using a serotonin isotope. A series of treatments must be given to Angelo over a certain space of time, and if he doesn’t receive each treatment, his condition will completely regress. Over the course of the treatments, Angelo improves drastically, regaining memories, abilities, and IQ. When Jarod discovers that Mr. Raines has done to another little boy what he did to Timmy, he and Angelo rescue the boy and try to synthesize another dosage of the serotonin isotope for him. They fail, and Angelo volunteers his final treatment. The little boy’s life and personality are saved, but Angelo’s sacrifice causes his complete and permanent regression back to his empathic state. Angelo is my hero.

Doctor Bashir and Section 31: In a Star Trek: Deep Space 9 episode that aired less than a month before “Crossover” takes place, entitled “Inquisition,” Section 31 approaches Doctor Julian Bashir about joining them, in the year 2374. He refuses. They try again several times but only succeed in making him determined to expose them. He is ultimately stonewalled by forces within the Federation during a major war. Perhaps with Jarod’s evidence, he will succeed, in an alternate timeline.

Inter Arma Enim Silent Leges: A later Deep Space 9 Section 31 episode shows Doctor Bashir leaving Space Station Deep Space 9 for a conference on the Romulan homeworld and ending up exposing an attempted Section 31 assassination on a Romulan official. The episode’s title is Latin for “In time of war the law falls silent,” a philosophy of ancient Rome and of Section 31 that claims war gives leeway for unlawful actions. Bashir contests that claim and the insinuation that the Federation is like the Roman empire. The episode aired in March 1999 and would have been filmed sometime that previous summer, a perfect time and a perfect theme for an episode for Jarod to be in as an extra.

Michael Westmore: Michael Westmore was makeup supervisor and makeup director for Star Trek: The Next Generation, Deep Space 9, Voyager, and Enterprise and worked on the four Next Generation movies as well.

Goes Nowhere, Does Nothing: In Star Trek: The Original Series, power relays aboard the Enterprise were often labeled with tiny labels to make them look official. As a joke, the set designers used the acronym GNDN, which they said means "Goes Nowhere, Does Nothing." Other jokes like this continued throughout all the series.

Jeffries Tubes: Jeffries tubes are maintenance shafts aboard Federation starships, designed to allow crewmembers to access ship's systems and to get around the ship in the case of a loss of power to the elevators. They were named after Matt Jeffries, the Original Series production designer who designed the look of the original Enterprise.