"I'm willing to make the occasional exception, but I am not about to turn this base into the Grand Central Station of the Multiverse!"
— Maj. Gen. Hank Landry
A time-space distortion resulting from a black hole causes dozens of SG-1 teams from alternate universes to arrive through the prime universe's stargate. Carter searches for a way to send them all back to their respective realities, but at least one of the alternate teams has their own agenda.
Last appearance of Dr. Janet Fraiser and Martouf/Lantash.
"Ripple Effect" provides examples of the following tropes:
- Alliance of Alternates: The Carters have to work together to save the day.
- Color-Coded for Your Convenience: The alternate teams who come through the gate are all wearing different colored camo, making it easy to tell them apart. Naturally, the "evil" team are the ones wearing black.
- Continuity Nod:
- When the first alternate team comes through, Lam speculates that they could be clones created by Ba'al.
- Alternate Mitchell suggests that he and his team could have been sent to a fake SGC designed to trick them, referencing the events of "Out of Mind."
- The black hole that the wormhole passes through is the one created by the Ori beachhead.
- Alternate Carter states that the wormhole anomaly is similar to the one encountered in "Red Sky".
- The Carters discuss the events of "A Matter of Time".
- Dead Alternate Counterpart: Inverted, with Janet Fraiser and Martouf, who have been dead for two and five years respectively in the prime universe, showing up very much alive as part of the desert camo team.
- Doppelgänger Gets Same Sentiment: Alternate Janet Fraiser and alternate Martouf meet our SG-1. Teal'c and Daniel have a very emotional reunion with Janet. With Martouf and Carter, the sentiment appears to go both ways, as alternate Martouf and his Carter continued a romantic relationship long after the point he was killed in our universe.
- Evil Twin: It's revealed that the black uniformed team deliberately engineered the whole plot in order to cross over to "our" universe and steal the ZPM powering Atlantis. Also lampshaded by Mitchell:Mitchell: You don't have beards so you're not from the evil twin universe, right?
- Expecting Someone Taller: Mitchell is slightly underwhelmed after meeting his first Asgard.Mitchell: You know, I read all the mission reports on the Asgard. They're not what I expected.Carter: What were you expecting?Mitchell: Well... Pants, for one.
- Expendable Alternate Universe: The black uniformed team play this trope straight, as they're willing to expose our universe to potential threats by stealing the ZPM in order to save their universe. Alternate Fraiser also calls Landry out on this, though it's ultimately subverted by the prime team when they give her the cure to the Prior plague to take back to her own universe.
- Finishing Each Other's Sentences: The various Carters lapse into this on a few occasions.
- For Want Of A Nail: A few notable differences between the various alternate universes are mentioned:
- Jacob and Selmak are both still alive in the black uniform team's reality.
- Alternate Carter mentions that in her universe they were unable to stop the Ori beachhead from forming and the Ori subsequently mounted an invasion of the Milky Way.
- Alternate Fraiser reveals that she also went on the mission to P3X-666 but she was never hit by an errant staff blast while stabilizing Airman Wells.
- The desert camo team never found a cure to the Prior plague, which has now reached pandemic levels on their Earth.
- Funny Background Event: At least a dozen different Carters from alternate universes milling around and eating blue jello as our Carter talks to Dr. Lee in her lab.
- Gambit Pileup: When the prime team and the black uniformed team are on the Prometheus, each trying to out-gambit the other in order to take control of the ship and enact their respective plans.Alt!Mitchell: Let me get this straight. We figured that you guys would try to escape and we set this trap for you, not realizing that you'd figure out that we'd figure you out and you'd set your own.
- Interrogation Montage: Used when the first alternate team to come through are questioned.
- Locking MacGyver in the Store Cupboard: After the prime team are locked in the brig of the Prometheus, Mitchell (actually alternate Mitchell in disguise) asks Carter whether she can hack the locks, to which she replies that she helped build the ship and escaping will be the easy part.
- The Main Characters Do Everything: Used to justify the fact that all the alternate teams coming through are versions of SG-1; Landry makes the decision to only let through teams that are under heavy fire, and Carter points out that as the frontline team, SG-1 is the most likely to get into that kind of trouble.
- Moment Killer: Kvasir interrupts Carter and alternate Martouf as they're about to kiss.
- Now Do It Again, Backwards: Used to send all the alternate teams back to their respective universes at the end of the episode.
- The Psycho Rangers: The black uniformed team are this for the prime team; they're not exactly evil, but they don't seem particularly bothered by screwing over their alternate universe counterparts either. This also serves as a nice Call-Back to the season 3 episode "Point of View", where Teal'c happily kills his alternate self in a different universe and states "ours is the only reality of consequence".
- Seinfeldian Conversation: Mitchell has a rambling conversation with his black uniformed counterpart about some Noodle Incident from their shared past involving "the spit-take of all spit-takes".
- Ship Tease: For Carter/Martouf and possibly Daniel/Janet, though it's mostly just giving closure to ships that have already been sunk in the prime universe. It's also mentioned that at least two alternate Carters are in a long-term committed relationship with somebody else; it's never explicitly stated who, but the clear implication is O'Neill. The Sam from the "Desert Camo" universe is apparently on maternity leave.
- Stealth Insult: After alternate Teal'c knocks Mitchell unconscious by slamming his head against a wall and choking him:Alt!Daniel: Wouldn't it have been easier just to zat him?Alt!Teal'c: Easier, yes. But far less gratifying.Alt!Mitchell: ...Did he just insult me?
- That's What I Would Do: Teal'c points out that they can anticipate the actions of the alternate team and get the better of them merely by thinking like themselves.
- Twin Switch: Alternate Mitchell switches uniforms with prime Mitchell, anticipating that the prime team will escape from the brig and wanting to observe how they do it. Fortunately, the prime team anticipate that he would do that, and plan accordingly.
- Well-Intentioned Extremist: The black uniformed team are trying to save their own universe, but they have no problem screwing over another reality in order to do so.
