Originally filmed as the series pilot. The decision was later made to move it further back into the season, requiring additional reshoots and editing to fit its new place in the season's story arc.
The number that Addison gives Ben for his mom's apartment in 1989, (212) 177-2350, isn't a valid North American telephone number. All exchanges must begin with a digit from 2 to 9; 0 and 1 are reserved for other purposes. Interestingly, the 555 exchange number, typical of film and television productions, was not used.
They find out that "Leaper X" is in the military and stationed at Camp Pendleton. In the TV show Timeless (2016), which dealt with time travel one of the main characters, Wyatt Logan (played by Matt Lanter) was Delta Force Soldier stationed at Camp Pendleton before going on the time trips.
This episode takes place in 1989 the Depeche Mode song Policy of truth wasn't released until 1990.
Ben Song is revealed to have an IQ of 197. While it's not definitive, as IQs are not empirically verifiable, this would theoretically make him one of the 30 smartest people ever known to have ever lived.