If the Langarans arrive somewhere and the camera dramatically reveals an Aschen, the new viewer shouldn't need SG-1 knowledge to be frightened. They should first encounter an extraordinarily pleasant, technologically sophisticated civilization offering exactly what Langara desperately needs.
Food technology. Medicine. Energy. Maybe even information about Earth.
The audience thinks, Finally, somebody helpful.
Jonas doesn't.
That's where the old continuity becomes delicious.
He quietly says:
"We're leaving."
The young team objects. These people haven't done anything.
"Jonas, they can help us."
"I know."
That's why we're leaving.
Now an old viewer knows exactly why the hair on Jonas's neck just stood up. A new viewer desperately wants to know.
And importantly, don't resolve the Aschen in that episode.
Leave.
The Stargate closes.
The Aschen representative watches it disappear.
Maybe asks an aide:
"Langara?"
"Yes."
"Interesting."
Then don't see them again for twenty episodes.
That's how an unwelcome guest should behave. 😄
The Vanir are perhaps even more interesting because forty years should have changed them. Don't simply reproduce the armored rogue Asgard from Atlantis. What has four decades without the main Asgard civilization done to them? Have they solved their genetic deterioration? Become desperate? Fragmented? Perhaps one faction regards the Tau'ri's inheritance of Asgard technology as theft.
And Replicators I'd be extremely stingy with.
One hand moving in the wreckage is worth more than an entire Replicator season.
Someone discovers a block.
McKay recognizes it.
His entire personality changes.
"Nobody touch that."
Our Langaran scientist:
"It's been inactive for decades."
"I didn't say it was active. I said don't touch it."
That's enough.
Because the really interesting question forty years later isn't:
Did the Replicators survive?
It's:
What did forty years of evolution do to something that can rewrite itself?
Maybe the answer is nothing. Maybe we never see them again. Letting some mysteries remain merely possible makes the universe feel enormous.
And there should be completely new villains—probably mostly new villains. Otherwise the Langarans are just cleaning SG-1's garage.
I'd probably use something like an 80/20 rule: roughly 80% of civilizations, adversaries, mysteries and problems are genuinely Langara-era discoveries; perhaps 20% have roots in the old universe.
That makes an old enemy showing up feel wrong in precisely the right way.
We've spent four episodes somewhere completely new.
Dial another address.
Beautiful countryside. Nice people. Advanced city.
The leader welcomes the Langarans warmly.
Jonas notices something growing in a field.
His expression changes.
Old viewers recognize it too.
Aschen.
