I Say What I Say

You meet yourself somehow, through Time Travel, dimension-hopping, cloning, or some even more exotic form of Applied Phlebotinum. Inevitably, if you spend enough time in the same room as yourself, the two of you will end up speaking in unison.

The implication isn't usually that there's any kind of mystical connection between the different versions of you. It's just that whatever you're saying is so characteristic of you that any possible version of you would have said it at that time.

See also Single-Minded Twins.

Film

 * A bizarre version occurs in Bill and Ted's Bogus Journey; the two aren't the same person, but they're so close in personality they might as well be; so when they split off to propose to the princesses, they read out the same speech, changing only the basic metaphor (one of them uses ocean life, the other forest; they even both have a 'no, that's fresh water' / 'no, that's the desert' moment in unison.
 * Similar to the above Bill and Ted trope, but for a blink-and-you'll-miss-it Not So Different: In Treasure Planet, when Jim is put in Silver's care, both pinch the bridge of their respective noses at the exact same time, then look up with the same expression.

Literature

 * The main character of The Probability Broach by L. Neil Smith does it on one occasion, when in the company of his alter ego from another timeline.
 * In Star Trek Department of Temporal Investigations: Watching the Clock, President Bacco is temporarily duplicated (long story). The two presidents respond to a compliment with a simultaneous "oh, please!" Amusingly, they also snark at each other for making the exact sort of grumpy, sarcastic comments that Bacco always makes.

Live Action TV
"Adelle: Finding him obstinate, are we? Topher and Victor: Yes! (pause) This is so weird."
 * In the Star Trek: Deep Space Nine episode "Visionary", O'Brien meets himself from five hours in the future. At one point they chorus "I hate temporal mechanics."
 * The Dollhouse episode "The Left Hand" sees Topher downloading a second copy of himself into Victor.

"Buffy: What if it doesn't work? Xanders: Kill us both, Spock! Willow: They're kind of the same now. Giles: Yes, he's clearly a bad influence on himself."
 * Stargate SG-1:
 * In "Tin Man", O'Neill and his robot duplicate get to chorus "For cryin' out loud!"
 * In "Fragile Balance", O'Neill gets cloned; his clone is a 15-year-old boy. When they meet up at the end of the episode and interrogate the alien who did it, they start answering him in unison. Eventually, the original O'Neill gets annoyed and tells his clone to knock it off.
 * In the Buffy the Vampire Slayer episode "The Replacement", Xander gets split into two beings. When they meet at the end just before being rejoined they have a tendency to speak together.


 * Done with actions in Heroes, such as Hiro being in the background of Young!Hiro as both push up their glasses at the same time in the same way.
 * Doctor Who:
 * When Mickey and his parallel-universe counterpart Rickey are running away from Cybermen in "The Age of Steel", they stop to catch their breath and each go off in their own panicked monologue, culminating in a unison recitation of "They know where we are!"
 * Done again in Series 6, with The 11th Doctor and "11.5", a clone created from sentient goo. They both have all the same memories and thought processes, leading to them almost always finishing the other one's sentences and saying the same thing at the same time. They actually don't mind, but it annoys Amy.
 * Played for drama in Farscape, when gets twinned, and the two talk and think so alike that when they resort to Rock-Paper-Scissors to decide which one is real, they end up spending several hours tied, before giving up.
 * In the Red Dwarf episode "The Inquisitor", Lister gets replaced by an alternative version of himself who never got to exist. When they meet each other, the original Lister is in the middle of trying to convince Rimmer of who he is, and the two end up chorusing "Rimmer, for smeg's sake!"

Western Animation
"Robot Leela: I have to go. This is just too freaky! (storms out) Fry: Please don't get upset, Leela. She's nothing like you! Leela: I have to go. This is just too freaky! (storms out)"
 * In the Animated Adaptation of Men in Black, when Jay first sees his quick clone, they say in unison "He's stunning!".
 * Futurama has a variant when Leela encounters her double; they're not actually simultaneous, but...


 * In Phineas and Ferb Across The Second Dimension, this happens three times between Dr. Doofenshmirtz and his more evil double in the other dimension. Each time, Doofenshmirtz-1 lampshades it by shouting "Jinx!" and claiming that Doofenshmirtz-2 owes him a soda.