In SG-1 and Stargate Atlantis, the prime method of destroying enemy ships is teleporting nukes right past their shield to blow them the hell out. You know, exactly like was done to the first Goa'uld ship in the entire 'Verse; Ra's, in the movie. After 15 years, still the most effective way. — Mr Death
Minor bit of Fridge Brilliance in the spin off Stargate Atlantis. In "Grace Under Pressure," McKay is hallucinating Samantha Carter as someone to talk to. At one point, she appears to him wearing a blue lace bra, and he thinks she's distracting him from finding a way to save himself, and calls her "Lt. Colonel Siren!" At first I thought he was just using Siren as a generic term for a beautiful, seductive woman, before I realized he was actually alluding to the original mythological Sirens who, As You Know, lured sailors to their deaths with their beautiful songs.
Even more minor bit of Fridge Brilliance mixed with Meaningful Name. The name Meredith means 'sea lord.' Which character on Stargate Atlantis is most associated with the sea? Rodney! He gets trapped underwater, names the whale that rescues him, and seems generally fond of sea life. Coincidence?
At first blush, the name "Wraith" for a race of chalk white life draining aliens seems both extremely unlikely and decidedly on-the-nose, until you learn the actual origin of the Wraith as Iratus bugs mutated by Ancient DNA, which means that the Wraith were likely named by the Ancients, who carried that memory with them when they returned to Earth, giving rise to the wraiths of legend.
While probably an example that could be relevant to other parts of the Stargate-verse too, the conclusion of the penultimate episode is particularly terrifying in its suggestions. Alt!Mckay states that the signal has traveled into all(?) alternate realities. So yes, the final episode ends on a high note with the super-hive being destroyed and Atlantis surviving. What about the countless other realities where the signal was picked up, and no one could stop the Wraith from slaughtering the population of Earth? In this instance, it may be best to follow Alt!Woolsey's advice and only be concerned about the safety and security of our own universe.
Since no one named Henry Hayes was our president, we are not in the Stargate universe. The Wraith are on their way.
In "38 Minutes", Dr. Weir and her colleagues dismiss Dr. Kavanagh's warnings that the Puddle jumper could explode if the stargate deactivated while the jumper was midway through, but Dr. Kavanaugh was absolutely right. In Stargate SG-1, we saw that Ernest Littlefield survived when the stargate was de-activated while he was in it and attached to a tether ("The Torment of Tantalus"), and the Goa'uld that was killed by a force-deactivated gate in another episode doesn't rule out the possibility that the back of his head was simply re-materialized elsewhere ("The Enemy Within"). The Puddle Jumper is a complicated piece of Lantean technology, and severing it down the middle could have caused an explosion given most aliens' preference for ships Made of Explodium.
The kawoosh has been used to perform such a severance, and no explosion occurred.
In "Inferno" it was stated that it would take the Daedalus 12 hours to get from the planet to Atlantis. It's been established that Pegasus is 3m light-years from Earth and that the Daedalus can travel there in three weeks. This implies that in 12 hours that Daedalus can travel (approximately) 71,429 light years. That's almost the entire diameter of the Milky Way Galaxy, let alone a dwarf Galaxy like Pegasus. Even if we assume the ship has to go slower through populated space than it can through the void between galaxies, Pegasus is still only about 4,000 light years in diameter. Not only does this beg the question of how any two points in Pegasus could be sufficiently far apart that it could take the Daedalus 12 hours to pass between them, but it also raises the question of how it could possibly be that the planet in the episode was that far away from Atlantis and yet the best option for evacuating the people was to fly to Atlantis in several trips rather than just dropping them off at a closer planet (ideally with a stargate but if not at least somewhere they could survive before the ship ferried them to Atlantis from there) and evacuating the people in a much shorter period of time. The only reason to have to take the people featured in the episode directly from the planet to Atlantis would be if there weren't any closer planets capable of supporting life. If the closest planet to Atlantis capable of supporting life was 12 hours travel away then either the Pegasus galaxy must be much larger than it is in reality (and certainly larger than the Milky Way) or the Daedalus should never be able to make the trip between galaxies at the speed it can.
Alternately, this planet is outside of the Pegasus galaxy, but part of the Pegasus galaxy network. Yes, colossal power sources are required to maintain a wormhole over intergalactic distances, but 71,429 light years is far more surmountable than 3,000,0000 light years.
Consider also the McKay-Carter Bridge of stargates built between Earth and Atlantis, which had 36 gates (34 gates in the Bridge with 1 gate for Earth and Atlantis). Since Midway had two gates which didn't connect between each other, there were 34 gaps between each gate (one between Earth and the first gate, 32 between each gate in the Bridge, excluding Midway, and one between the last Pegasus gate and Atlantis). This means each pair of stargates can create a wormhole at least 88,000 light years apart, probably with a tolerance of greater distances for engineering reasons. A gate being 71,000 light years away from Atlantis is still reasonable.
The bigger question is why evacuating all the way to Atlantis if you are under time constraint. You can simply put the people down on the other side of the planet and spend the next month evacuating them. Sure a super volcano exploding will destroy the ecosystem eventually, but the oxygen wouldn't run out for months to come. Another simple fix is grabbing another gate from somewhere else temporarily.
During the episode "Phantoms" the DHD was destroyed trapping the team on an alien planet. There's nothing unusual about that. At the end, once the situation was resolved, they then had to wait around for the Daedalus to come and collect them and take them (some of them wounded) home. However, it's been shown repeatedly in SG1 that it's possible to manually dial a gate as long as you have a power source. So why didn't Weir just sent a generator through and let them dial Atlantis with that. For that matter, why not just fly a Puddle Jumper through and use its inbuilt DHD to dial the gate?
You can't manually dial Pegasus gates, they don't have the spinning inner ring. And there were too many trees round the gate to fit a puddle jumper.
The first point is certainly true, but if you look at the shot from when they first walked through the gate there was an open space with no trees in front of the gate with plenty of room to fit a jumper.