Using the Odyssey, the team plus Landry travel to the Asgard home galaxy, where Thor tells them that they intend to pass all of their knowledge onto the Tau'ri before committing mass suicide rather than wait for the effects of their Clone Degeneration to kill them off slowly. After receiving the Asgard upgrades, the ship is quickly set upon by an Ori fleet, and Carter is forced to activate a time dilation field in order to buy them more time after they fail to evade their pursuers; however, it ends up taking much longer than she anticipated to work out a solution, and the team become trapped on the ship for fifty years.
"Unending" provides examples of the following tropes:
- Aborted Declaration of Love: The final exchange between Daniel and Vala before the timeline is erased:Daniel: I want you to know, even if you are gonna forget, that I wasn't with you all these years because we were trapped on this God-awful ship. I was with you because...
Vala: I know. And I want you to know that I—
Daniel: I know. I know.
- Actor Allusion: When Thor beams onto the ship, Vala asks how the others can tell the Asgard apart, to which Daniel replies that it's "the voice"; Michael Shanks, who plays Daniel, also provides the voice for Thor.
- And the Adventure Continues: The episode, and the series, ends with the team stepping through the Stargate for another mission.
- Back for the Finale: The Asgard and specifically Thor, who hasn't been seen since the late Season Eight. Unfortunately it's also a case of Back for the Dead, since the only reason he shows up at all is to bestow the knowledge of the Asgard upon the team before they commit mass suicide.
- Big Damn Kiss: Between Daniel and Vala, after the mutual realization that they actually do have serious feelings for each other.
- Bittersweet Ending: After the team is trapped on the Odyssey for fifty years, Carter works out a way to reverse time and they manage to avoid getting hit by the Ori weapons fire - but everything that took place on the ship, including Daniel and Vala's relationship, is effectively erased, and Teal'c has to stay old to prevent them from making the same mistake all over again.
- Also humanity is declared to be "The Fifth Race" by Thor, the Asgard give all their technology to humanity and we see that Earth finally has weapons strong enough to directly fight the Ori and win. But the Asgard all die out in a mass suicide to prevent a slow painful death of their people and so that their technology will not fall into the wrong hands.
- Borrowed Catchphrase: Becomes the penultimate line of the entire series, with Mitchell, Carter, Daniel and Vala all chiming in with Teal'c's "indeed".
- Bottle Episode: Oddly enough, for a series finale; apart from the final scene, the entire episode takes place on board the Odyssey and only features the core cast.
- Call-Back: Many:
- SG-1 inadvertently leads the Big Bad to the homeworld of one of the Four Great Races, leading to that planet blowing up. This time, it isn't a Fake Action Prologue in a TV script.
- Mitchell is frequently seen sparring with Teal'c using the Sodan fighting technique.
- Thor declares that the Tau'ri have finally taken their place as the Fifth Race.
- Carter hugs Thor again.
- Mitchell repeats his speech from "Flesh and Blood" about being all for fighting to the death so long as they have a plan.
- Daniel's obsession with the Asgard knowledge core despite the fact that he'll never get to share it with anyone is similar to his attitude regarding the "meaning of life stuff".
- Daniel's "you better not be messin' with me" after he kisses Vala is a call back to "The Ties That Bind", where she appeared similarly upset by his rejection; the difference being that on that occasion she was messing with him, while here she's a hundred percent serious and they get together.
- Mitchell and Landry are shown playing chess on a few occasions while they're trapped on board the ship.
- Character Death: Thor and the rest of the Asgard race commit suicide after bequeathing their collective knowledge to humanity.
- Chekhov's Boomerang: Carter uses the Asgard time dilation device to slow down time on the ship while she figures out a way to avoid the Ori weapons.
- Continuity Nod:
- At the beginning of the episode, Vala complains that the last time she was this bored, she took hostages, to which Daniel replies that "he was there".
- Mitchell asks why they can't just evacuate the ship in the F-302s, as that's how he escaped from the Korolev when it was destroyed.
- Mitchell discusses the events of "Line in the Sand".
- Crew of One: Landry orders the evacuation of the Odyssey's crew before they make their last stand against the Ori motherships, leaving just six people to man the entire ship. This leads to some vaguely creepy scenes with Mitchell jogging down totally deserted hallways.
- Death Is Cheap: Landry eventually dies of old age after the first twenty or so years on the ship, but he gets better when the timeline is erased. Additionally, the entire team dies (bar Teal'c, who is shielded to ensure he survives and gets the ship away the 2nd time around) for a split second when the energy from the Ori weapon hits the ship, before time is reversed.
- Dénouement Episode: The main story threads were dealt with in the previous episode, while this one is mostly a standalone dealing with the characters and their interpersonal relationships.
- Despair Event Horizon: The entire team descends into one after Landry's death.
- Deus ex Machina: Discussed when Mitchell says that their problem could be solved by having Superman come to fly the ship to safety.
- Double-Meaning Title: In addition to the obvious meaning of the frozen time in the time dilation field, this is also the last episode of the series, but since its cancellation was announced before they could wrap up the Ori plot, this series finale is an ending that doesn't actually end the story, hence, an "un-ending".
- Dramatic Irony: Carter lampshades this when she finally figures out how to reverse time after fifty years, only to realize that they don't have enough power to pull it off after sustaining the time dilation field for so long.Carter: There's irony for you, huh? I create the field to buy us more time, I finally figure out how to undo it all, and that extra time is what makes it impossible.
- Earth-Shattering Kaboom: The entire Asgard planet blows up at the beginning of the episode.
- Face Death with Dignity: The Asgard finally run up against the limitations of their cloning technology and decide it's time to finally end their entire race. But not before giving one final, gigantic gift to humanity.
- Foreshadowing: After they've been on the ship for a few months, Vala makes an offhand comment about it being a pity that they can't reverse time to prevent them from activating the time dilation field in the first place. At the end of the episode, that's pretty much what they do.
- Friendship Moment: At least some attention is paid to most of the major relationships, but there are some particularly poignant moments between the original members of the team, with Carter confiding in Daniel that she's given up on finding a solution and later being comforted by Teal'c after Landry dies.
- Frontline General: Landry takes command of the Odyssey for the duration of the episode.
- Grumpy Old Man: Mitchell and Daniel both turn into this after fifty years.
- Heroic Sacrifice: Teal'c volunteers to remain outside the field when time is reversed, meaning that he stays old. He claims that he's the most logical choice as he has a longer lifespan than the others and doesn't really show any visible signs of aging beyond the white streak in his hair, but the others don't take his decision lightly as Mitchell points out that he's still lost as many years as the rest of them.
- History Repeats: The whole reason one of the team has to stay old is that somebody needs to remember the events of the last fifty years or there'll be nothing to stop them from making the same mistake and activating the dilation field all over again.
- Hoist by His Own Petard: The Asgard's attempts to cheat death via cloning is the very thing that ends up dooming them.
- Hurricane of Aphorisms: The team indulge in this as they prepare to leave for their next mission at the end of the episode, trading cliches that sum up their experiences:Daniel: Beggars can't be choosers. Better late than never. Look before you leap...
Mitchell: The best things in life are free.
Vala: Let me guess: "beauty is only skin-deep"?
Daniel: Silence is golden.
Mitchell: Jack of all trades, master of none.
Carter: Nothing ventured, nothing gained.
Vala: Life is too short.
Teal'c: Good things come to those who wait.
- Hyperspeed Escape: The team do this repeatedly to try and escape from the Ori motherships pursuing them before realizing that the newly-installed Asgard core allows the ships to track them in subspace.
- I'm Dying, Please Take My MacGuffin: The Asgard bestow all of their knowledge and technology upon the team before committing mass suicide.
- Incurable Cough of Death: As the oldest member of the cast, Landry develops one after about twenty years on the ship, and dies shortly afterward.
- It's All My Fault: It's shown repeatedly throughout the episode that Carter blames herself for stranding the ship in the time dilation field, despite the fact that if she hadn't acted when she did, they would have been destroyed by the Ori weapons.
- Matter Replicator: Carter is able to modify the Odyssey's beaming technology to generate matter including food and other vital supplies for the duration of their time on the ship.
- Meaningful Echo: "Life is too short", which is repeated three times throughout the episode and associated with Daniel and Vala's relationship. The first time, Daniel is lamenting the fate of the Asgard in a conversation which ultimately leads to he and Vala getting together; the second time is after the first Time Skip, when they've been together and stuck on the ship for twenty years, with Vala sarcastically asking if Daniel still thinks that now. The phrase is then repeated for a third and final time after the timeline has been erased, when Vala rattles it off among a series of cliches as the team prepares to embark on another mission, causing Daniel to look at her oddly.
- More Hero than Thou: Carter initially states that she should be the one to stay old when time is reversed, but Teal'c insists on doing it instead as he has longer to live.
- Mundane Utility: Carter uses the fifty years as an opportunity to learn how to play cello, something she claims she's always wanted to do, while Landry devotes his time to cultivating a garden. He also quips that the team can use the time to catch up on their paperwork when the field is first activated.
- My God, You Are Serious!: Daniel's expression when he realizes that his "The Reason You Suck" Speech to Vala genuinely hurt her, and that he had misinterpreted her expression of sincere feelings.
- Nice Job Breaking It, Hero: Carter's attempt to buy more time to find a way of evading the Ori weapons fire results in the team being stranded for fifty years.
- "The Reason You Suck" Speech: Daniel launches into an absolutely vicious diatribe detailing all the reasons why Vala sucks after she propositions him again, though he does seem to regret it when he realizes that a) she's actually hurt by it and b) she does have serious feelings for him.
- Relationship Upgrade: Daniel and Vala get together and spend fifty years in a stable and loving relationship until it gets erased at the end of the episode.
- Reset Button: Everything that happens during the fifty years spent on the ship is erased when time is reversed. Played with somewhat, since the loophole allowing Teal'c to remain old means that he still remembers everything even if it technically never happened.
- Rewind Gag: The episode plays this trope more seriously. SG-1, aboard the Tau'ri vessel Odyssey, activates an Asgard Time Dilation device to avoid being destroyed by an Ori warship's energy weapon, and spend decades coming up with a plan to save the ship and its repository of advanced knowledge given to them by the Asgard from destruction. They finally come up with a way to channel energy from the beam weapon to quite literally rewind time to a point before their destruction, so that Teal'c can prevent the ship from getting hit in the first place.
- Sanity Slippage: Self-confessed Type-A Mitchell does not react well to being cooped up on the Odyssey and begins to act increasingly erratically the more time passes. One particularly dark scene has him sitting in one of the F-302s, apparently considering leaving the time bubble despite the fact it would almost certainly kill him. He even lampshades this at the end of the episode:Mitchell: You know, I like to imagine I handled myself well, but I think I went a bit crazy cooped up on that ship for so long.
- Sexy Discretion Shot: When Daniel and Vala consummate their relationship, the scene cuts from them kissing passionately and falling out of shot to Vala leaving Daniel's room looking somewhat disheveled as a bemused Mitchell jogs past.
- Sitting Duck: Mitchell describes the Odyssey as such while it's stuck in the time bubble:Mitchell: I hate this ship.
Landry: You're a pilot. You love flying.
Mitchell: In fighters. This is not flying, this is literally sitting still. This is the Love Boat without the buffet and the band.
- Space Madness: As seen in Sanity Slippage above, Mitchell does not take well to being trapped on a ship in a time dilation field.
- Stealth Insult:Vala: I'm hearing things all the time. Are you hearing things?
Teal'c: I am trying not to.
- Suicide Pact: The Asgard all agree to commit mass suicide rather than dying slowly as a result of disease from centuries of Clone Degeneration.
- Surprise Party: Vala gets the crew to throw one for Daniel at the beginning of the episode, only for him to respond that it's not his birthday and tell her to entertain herself some other way.
- Taking You with Me: Played for laughs; on hearing that they're going to be stuck on the ship for at least a few months, Vala immediately turns to Daniel and hisses that she's going to go crazy and she intends to take him with her.
- Tantrum Throwing: Mitchell destroys his room in a fit of rage at one point.
- Time for Plan B: Discussed when Carter tells the others that trying to take the ship out of phase isn't an option:Mitchell: Okay, time for Plan B
Carter: Actually, I ran that simulation too. If we beam ourselves into the buffer ready to transport down onto the planet and set the time dilation field to deactivate on a timer, the matter stream still doesn't have enough time to fully exit the buffer and get clear of the explosion.
Mitchell: Fine, Plan C.
- Time Passes Montage: The episode uses one set to Creedence Clearwater Revival's "Have You Ever Seen The Rain?" to reflect the passage of the first twenty years, with scenes including at least one Christmas dinner, Mitchell sparring with Teal'c and going steadily more stir-crazy, Vala sobbing in Daniel's arms after suffering a miscarriage, Carter trying to find a solution to the problem and practicing the cello, and Landry tending his garden.
- Time Skip: Used after the first twenty years and then after the first fifty.
- Under the Mistletoe: Mitchell exchanges platonic mistletoe kisses with both Carter and Vala during the Christmas dinner scene.
- Wham Line:Landry: What is it you're planning on giving us?
Thor: Everything we have and know.
- Year Inside, Hour Outside: In the space of a fraction of a second, the team inside the time dilation field live for fifty years.
- You Are Not Ready: Utterly subverted by the Asgard, who give all their knowledge and technology to the Tau'ri and proclaim them to be the Fifth Race.