This is the first appearance of the Axanar, a species mentioned but not seen in Court Martial (1967) and Whom Gods Destroy (1969). They went on to appear only once more, in the form of a corpse in Dead Stop (2002).
The trim color on the uniform's shoulders are precursors to the shirt colors on the original show. Red: Engineering, Security and Communications; Blue: Science and Medical; Yellow: Command.
An outtake has Scott Bakula kneeling down, saying, "something's squeaking. I think it's coming from underneath the deck plating. But every time I get close to it, I... I have to start the scene over." Jolene Blalock, who is standing over him, starts laughing a few seconds later, realizing what he has said.
In the show's opening credits, there is a "mystery ship" that appears between the shot of Zefram Cochrane's Phoenix and Captain Archer's Enterprise. The mystery ship has a more primitive layout than the Enterprise, and huge blue impulse engines. This ship has never been named, and no explanation has been given as to what its function is, although some fans speculate that it may be the S.S. Valiant mentioned in Where No Man Has Gone Before (1966).
This is the first episode to feature EV suits: costumes that subsequently appeared, occasionally, through the run of Enterprise.