Your Universe or Mine?

A person from one universe (of The Multiverse) falls in love with someone from an alternate universe. Or a Time Traveller falls for someone in the period he's visiting, or vice versa. The dilemma for the Time Traveller or dimension-hopper is how far to pursue the relationship: Maintaining such a relationship often means that one of the parties involved will have to give up his own life in his own universe or timeline to fit into the other's.

May result in Star-Crossed Lovers. Compare Stay With the Aliens and Time Travel Romance.

Anime

 * Fushigi Yuugi
 * Inuyasha.
 * In Zero no Tsukaima Saito is summoned by Louise to alternate world.
 * Vision of Escaflowne:
 * Brigadoon Marin and Melan ends with this choice.

Comics

 * Toyed with and ultimately discarded for the DC vs Marvel Universe crossover (the big one that lead to the Amalgam comics), where Jubilee and Tim Drake(Robin) struck up a rather sweet mini-romance that made them having to fight each other rather difficult. Due to the whole thing having since been quietly shuffled away, only a few remaining shippers remember what might have been.
 * Perhaps not quite the same thing, but in the Justice League/Avengers crossover the anthropomorphic representations of the DC and Marvel universes fall for each other only to be forced apart at the mini-series' end.
 * The comic had a straight example with Hawkeye, in an Alternate History, ditching his universe to be with Black Canary (a Shout-Out to the way Canary herself switched Earths in the Bronze Age, although she did that because she had lost, rather than gained, a lover).

Fan Works

 * In On a Cross And Arrow, both Fluttershy and Rarity end up falling in love with their male counterparts (Butterscotch and Elusive, respectively). Meanwhile, Applejack and Rainbow Dash seem to be sweet on each other's male counterparts, Rainbow Blitz and Applejack. There's also a hint of this with Celestia and her Rule 63-universe counterpart, Prince Solaris, at the end.
 * In the JLA Watchtower universe, Starfire and Hugo. A bit of background: Watchtower was a spin-off of Livejournal roleplay Lunatic Cafe, which was a multiverse crossroads. One of the Watchtower players had a character for the Lunatic, a universe-displaced, alternate timeline version of Hugo Weaving who had been slated to die in a traffic accident, but was snatched to the Lunatic. In a plot that crossed both games, an injured Nightwing stumbled into the cafe after an incident on Watchtower. Hugo was the first to intervene and saved Nightwing's life. When Nightwing's friends from Watchtower came to take him home, that universe's version of Starfire took a fancy to Hugo. A whirlwind courtship later, "Hugo Wallace Anders" was set up with a new life and identity in Watchtower-verse.

Films

 * Somewhere in Time hinges on this.
 * Kate and Leopold depends on this as well.
 * It's key to Enchanted as well.
 * Doc Brown and Clara Clayton in Back to The Future Part III have something like this, but the fact that Clara was supposed to have died (and survived only through Doc's timely intervention) may help simplify matters.
 * In the end the seem to choose option C. Live sort of outside of time traveling through the past and future with their flying train.
 * Due to some other time-related shenanigans in The Game,
 * In fact, the same actress (Mary Steenburgen) faced a similar decision in Time After Time. Playing a modern woman who falls in love with H.G. Wells on his trip to the 20th century, she finally decides to return with him to the 1880s. "I'm not makin' any promises, but when we get back, I'm changin' my name to Susan B. Anthony".
 * The Film of the Book only of The Chronicles of Narnia: Prince Caspian has this between Caspian and Susan, who are from different worlds, but have no romance at all in the original books. Interestingly, the Pevensie siblings never married in all the years they ruled Narnia, despite all but forgetting they came from another world and despite The Lion, the Witch, and the Wardrobe mentioning Susan and Lucy having many, many suitors (but the only one we ever meet personally is a haughty, evil prince).
 * In Star Trek IV the Voyage Home, Dr. Gillian Taylor (the scientist responsible for taking care of the whales) chooses to go with Captain Kirk to his time - then promptly leaves him. Kudos to her for staying alive, though.
 * She seemed to have chosen to go to the future primarily to be with the whales rather than Kirk.
 * There is a short, but deep, version of this in the original Terminator. The time machine is only one way though, so it's not like the guy had much of a choice after he arrived.

Literature

 * In Alan Dean Foster's The Time of the Transferrance, Spellsinger Jon-Tom must choose between returning to our world and remaining in the warmlands, where his wife, friends, and magical abilities are.
 * An issue for Lyra and Will in His Dark Materials, though subverted as one can't live in the universe of another for long and
 * In Nora Roberts' Circle trilogy, each set of lovers is either from a drastically different period of time from each other, or from two different worlds.
 * In Princes Nevermore by Dian Curtis Regan, Princess Quinn finds herself in the Human world- and there falls in love with a human boy. however, she is informed that  in the end, she
 * In The Secret of the Unicorn Queen, Sheila and Darian try to tell each other how they feel, but  Later, When they are reunited, Sheila must decide if she can go back to her ordinary life, or if she should stay with him. she choses to   but
 * In the Star Trek Expanded Universe novel Stargazer: Three, Andreas Nikolas is secretly infatuated with the Asmund twins. Unfortunately, Gerda and Idun were raised by Klingons (also, one of them is already in a relationship). The Stargazer's transporter then deposits an alternate universe counterpart to the twins named Gerda Idun Asmund on the ship. Unlike her duplicates, she was raised by humans and is much more friendly. He instantly falls for her, and she returns his affections. Unfortunately, she is an agent from the Mirror Universe, send to steal the ship's chief engineer as a last-ditch effort to save the Terran Empire from The Alliance. When her subterfuge is discovered, she tells Nikolas that, in her universe, they were lovers until he was killed in battle. He lets her return to her universe but wants to join her. She leaves alone but breaks down into tears on the other side. The next novel shows that this has had a tremendous impact on Nikolas and he eventually resigns.
 * In Barbara Hambly's Windrose Chronicles, ends up  the Empire of Ferryth, and crossing the Void to stay with  in 1980s Los Angelos.
 * This turns out to be something of a problem, because Earth has no magic. The implications of living in a magicless world are further explored in Dog Wizard and the short story Firemaggot.
 * The magic situation becomes even more of a problem at the end of Dog Wizard, when it's revealed that
 * The magic situation becomes even more of a problem at the end of Dog Wizard, when it's revealed that

Live Action TV
"John: There's no wormhole. There's no home. There's only you..."
 * Sliders had this come up more than once.
 * In an early episode, a No Celebrities Were Harmed version of Mrs. Fields fell in love with Quinn in a universe which was dangerously short on men. Quinn slid off and left her.
 * In another, the one with the Malthusian lottery, both Rembrandt and Wade get involved with people in that universe. (Or rather, someone from that universe gets involved with Wade.) Rembrandt's interest would rather die (she's looking forward to it) than slide off, and is looking forward to his joining her; Wade's interest helps rescue them and slides off with them -- though, since this was a Season Finale, he is dropped with only a Handwave at the beginning of the next season.
 * And in the third season, Maggie gives up an adopted universe, and Quinn gives up a short trip to his home universe, for each other.
 * In Farscape, John has to choose between Earth and Aeryn.


 * In the Star Trek:TNG episode "Yesterday's Enterprise," (an Alternate Universe version of) Tasha Yar returns to the past with Lt. Richard Castillo on the Enterprise-C.
 * At the end of Sy Fy's Alice Alice and Hatter have an awkward goodbye where they lightly suggest one of them could sometime visit the other one's world. It doesn't take long for Hatter to show up at Alice's door.
 * In Neverwhere, Richard Mayhew is offered the choice between his normal life in London Above and his new life in London Below twice. The first time, he doesn't really understand the choice  The second, he returns to his normal life...
 * In Life On Mars, Sam  only to change his mind and
 * Also slightly subverted in Ashes to Ashes it isn't really much of a choice for Alex; she wants Gene, but wants to go home to her daughter more
 * The ending of Lost in Austen sees Amanda staying inside the world of Pride and Prejudice to be with Darcy -- after having systematically burned all her bridges there because she was planning on returning to the 21st century.
 * Fringe plays with it a bit in the second season finale.

Theater

 * Happens at the end of Brigadoon.

Video Games

 * In Star Ocean: The Second Story, some of the recruitable heroes weren't born on Expel, coming from other planets and space-faring cultures. Depending on your Relationship Values, this can lead to one side of a given pairing choosing to stay on Expel to be with their loved one, or the other member deciding to accompany them into space, leaving behind their old life in the process.
 * Same in the third installment: Fayt can stay on Elicoor with Albel or Nel, travel to Klaus with Cliff or Mirage, or head off to some as-yet-unknown place with Maria.
 * Iron Man when placed opposite of pretty much any female character in Marvel vs. Capcom 3. This ranges from Crimson Viper to Tron Bonne to Hsien-Ko to Morrigan. The only exception? Amaterasu, who is a dog.
 * I am honestly surprised that stopped him.

Web Comics

 * Torg has had this a couple times in Sluggy Freelance. First when he time-traveled to medieval Europe and met Valerie before she became a vampire. At first he tries to pursue a relationship with her, but backs out upon discovering that the UST he'd had with vampire Val in his modern world was only because he looks like (and may be the reincarnation of) her dead husband. Later, when he spends a long stretch of time in the Dimension of Lame, he hooks up with that universe's version of Zoe. After that, Torg realizes that Alt-Zoe was also just using him to replace a dead husband, namely her own dimension's version of Torg. He also realizes that she's still not the same as the Zoe from his dimension, the one he's really in love with. Pete Abrams just does not seem to want Torg to get any extra-dimensional love.
 * Just extra-dimensional? It's been ten years and the poor guy still can't catch a break, even with his universe's Zoe. Then again, things are beginning to look up for him.
 * Were the above comment in the slightest bit funny, it would be the biggest Funny Aneurysm ever.
 * In this Supernormal Step Van discourages Akela from pursuing a relationship with Fiona because of this trope.
 * Brunhilda in The KA Mics is dating Bobby (Life) from Life and Death.
 * Dark Eyes from Magical Misfits got pregnant by Brian from Prismatic Vodka.
 * In Homestuck, at least a third of the extra-dimensional aliens have fallen for various human characters, and vice versa. They seem to be taking a third option, and creating a new universe entirely for all of them to live in.

Western Animation

 * Happens in the second Jimmy Neutron/Fairly Oddparents crossover entitled "Jimmy Timmy Power Hour 2: When Nerds Collide". The obvious solution, since both shows run off the Twin Rules, is to throw an interdimensional dance party.