According to Sean Murray, Tony DiNozzo's quote of the line "In a world weary of wars..." from an unnamed movie was made up by Michael Weatherly.
When Abby and McGee are briefing Gibbs on the impostor's work at an IT lab, the music playing quietly in the background is the Knight Rider (1982) theme. Knight Rider was based around a man living under an assumed identity.
The episode's title Blast from the Past (2015) is not only a reference to Gibb's past as an undercover agent, but also a reference to Mark Harmon's past as an actor. We see Harmon once again portraying a doctor, a role that helped start his acting career in the early 80's when he played the part of Dr. Robert Caldwell in St. Elsewhere (1982).
The house that they go into at around the 30-minute mark appears to have been filmed in the same house as the houses that appear in Season 7 Episode 21 and Season 9 Episode 15.