Star Trek: Enterprise, being a prequel series, did this a lot:
- The Xyrillians are shown to have advanced holography in "Unexpected" that is unlike anything humans have seen before. Several of the devices end up in the hands of the Klingons. As Starfleet vessels are not equipped with holodecks until after the Klingon Empire allies with the Federation, it is very likely that this is where the technology originated.
- Archer makes a pretty accurate prediction of the Prime Directive in "Dear Doctor":"Someday my people are going to come up with some sort of a doctrine: something that tells us what we can and can't do out here – should and shouldn't do. But until somebody tells me that they've drafted that directive, I'm going to have to remind myself every day that we didn't come out here to play God."
- In the same episode, the Valakians mention having made contact with the Ferengi, whom the Enterprise crew has never heard of. Four Ferengi merchants appear in the episode "Acquisition," but the crew never learns much about them, including their species name, because the official first contact will not happen for several centuries.
- In "Sleeping Dogs," members of the crew first discover photon torpedoes on a Klingon warship, which will later become standard issue on Federation starships.
- In "Oasis," the crew find a colony in which only two people are real, the rest are holographic representations of dead people. Archer tries to encourage them to leave by arguing "What will you do if one of you gets sick? Create a holographic doctor?"
- "Singularity" had Malcolm Reed working on an automatic tactical alert procedure. Trip refers to it as "Reed Alert".
- In "Horizon," Travis says that Starfleet should consider putting families on starships. Malcolm scoffs at this idea. After all, what's next? Having a psychologist on the bridge?
- On finding out that the Borg have adapted to their phase pistols in "Regeneration," one character remarks that "we might as well have been firing holographic bullets". To clarify, a holographic gun was how Picard killed two drones in First Contact. At the end of that episode, Archer finds out that the Borg managed to send a subspace transmission to the Delta Quadrant. He estimates that it'll take about 200 years for it to reach its destination. Two centuries later, Picard makes contact with the Borg after a number of Starfleet outposts are destroyed.
- An Organian secretly observing the crew in "Observer Effect" predicts they'll have barely 5000 years to prepare for First Contact with humanity, the joke being that we know it'll happen a lot sooner (TOS "Errand of Mercy").
- T'Les' criticisms of her daughter T'Pol's relationship with Trip Tucker are particularly poignant, knowing what we do about Spock's troubles regarding his own mixed parentage."Do you really believe that a human and a Vulcan can have a future together? Imagine the shame your children would endure, assuming that the two of you could have children."
