Sarah Silverman was considered to join the regular cast for the fourth season, after executive producer Brannon Braga enjoyed her work in this two-part story. But he eventually chose Jeri Ryan to join the cast instead.
The Chronowerx logo is the same as the Federation insignia from the 29th century, as seen on Captain Braxton's comm badge.
The black-and-white photo of Nixon and Starling shaking hands is the famous one of Elvis Presley and Richard Nixon from December 21, 1970, retouched.
First mention of a future Starfleet that monitors and repairs the time-line.
Janeway refers to late 1990s computer technology as "stone knives and bearskins" per Spock in The City on the Edge of Forever (1967).