Two characters are, as far as the audience are concerned, not romantically involved with each other. Maybe they're Just Friends, co-workers, or perhaps even strangers. Then those characters get Put on a Bus, or become Out of Focus, or maybe the story gets a Time Skip. And when the audience see those two characters again, they're already together, maybe even married.
Basically, this is an inversion of an Offscreen Breakup, where the writers can justify pairing the two people together without having to dedicate a Romance Arc around them. It is commonly invoked to prevent a Romantic Plot Tumour (if the story is not centered around romance), but could also lead to accusations of Strangled by the Red String if not handled carefully.
Compare Married in the Future, where characters who are already in a relationship consolidate their ties after a Time Skip or in an Alternate Universe, and Last Minute Hookup, where characters are abruptly paired off in the finale, but the upgrade doesn't necessarily have to happen off-screen.
Note: This trope only counts when the couple has a Relationship Upgrade in mid-story. It doesn't qualify if they are introduced as a couple from the get-go.
- Most pairings in Dragon Ball and its continuities (though Gohan/Videl actually averts it, since the two take a while to develop their feelings). A few characters marry and have kids during the series's frequent time skips with little on-screen development. To the author's credit, the reason for the lack of development is because he's stated in interviews that he doesn't care for romance, and most of the couples hook up during a Time Skip of several years, allowing the readers' imaginations to run wild.
- In Lyrical Nanoha, Chrono and Amy go from snarky colleagues to married-with-two-children during the Time Skip between A's and StrikerS seasons, though some off-handed comments imply this was more of a Shotgun Wedding. Likewise, Griffith and Lucino complete their romance arc off-screen between StrikerS and Force and are married in the latter.
- Downplayed by Asuma and Kurenai in Naruto, since they at least have one moment where they're walking together and Kakashi accused them of dating (which they try to deny). After the Time Skip, we only see they're married after we see Kurenai with a wedding ring... and not long after that, Asuma died in battle by Hidan's hands.
- Played straight by the parents of Inojin whose parents had one misleading interaction during the series, Chocho whose parents never interacted at all and Metal Lee who's parents consist of Rock Lee and an unknown person.
- One Piece: Oda has stated that he isn't very good at writing romance, so this is to be expected; one example is how Mr. 9 and Miss Monday hooking up with a child after the Time Skip when, in their previous appearances, they only interact as fellow members of Baroque Works. Subverted, however, by Rebecca's parents Kyros and Scarlet; there's a dedicated flashback story about how the two get together, even if it's mostly shown in short romantic montages.
- In Diamond and Silver's Excellent Adventure, Twilight Sparkle's very first scene with Baron Zeppeli—at the end of the fic—establishes that they've been a couple for some months, offscreen. (Time travel was involved.) Mainly this came about because the entire fic was a Round Robin, and the author who wrote this part thought a sudden relationship between them would be funny.
- Tonks and Lupin were revealed to be in love at the end of Harry Potter and the Half-Blood Prince. Neither Harry nor the audience saw the relationship develop, so this comes as quite a surprise — especially since, in the beginning of the book, Harry actually thought that Tonks was in love with Sirius instead because she started behaving strangely after his death. The two got married some time between the sixth and seventh book, but the event was only given a brief mention in the prologue of The Deathly Hallows.
- Downplayed in Ramona Forever. Aunt Bea mentions that she and Mrs. Quimby used to go to the same school as Howie's visiting uncle, Hobart, but otherwise made no indication that the two personally know each other — and, as far as Ramona is concerned, her aunt is seeing a man named Michael. Partway through the book, there were talks about Howie's uncle starting to date a teacher, whom Ramona suspects is her Aunt. This was later confirmed on-screen when Uncle Hobart and Aunt Bea shows up at dinner and announce that they're getting married. Even though the readers are given plenty of foreshadow regarding the couple's relationship before its reveal, they still did not see how exactly their romance unfold. At least the wedding takes place on-screen though, and the occasion serves as the book's climax.
- It's implied that at some point between when Skitter turns herself in to the Protectorate and later becomes the superhero Weaver, and the final battles with Scion that her henchmen Forrest and Charlotte became a couple.
- The supervillian mercenaries Gregor the Snail and Shamrock are seen as part of Faultine's crew in the beginning, but there's no hint of romance between them. By the time of Faultline's Interlude around the midpoint of the story, however, they're seen holding hands and are implied to have become a couple offscreen.
- In Further Tales of the City, Mary Ann and Brian, previously portrayed as just housemates, are shown to have become engaged since the end of the previous book.
- In the early seasons of Monk, there was a bit of Ship Tease between Sharona and Randy (she happened across a personal ad he had placed matching her description), but for the most part, they were simply portrayed as somewhat argumentative friends. In the last episode, it's revealed that Randy is moving departments to be close to Sharona, with whom he's apparently become involved offscreen.
- Seinfeld: Jerry and Elaine dated at some point prior to the series and are now Just Friends. The reason why they broke up is never explained.
- Doctor Who had Martha and Mickey unexpectedly start a relationship somewhere between "The Stolen Earth"/"Journeys' End" and "The End of Time", even though Martha had previously been depicted as being engaged to a different man.
- The epilogue of Eternal Eden has party members Fierro and Josefine engaged to one another, despite not having any romantic interactions throughout their journey together, owing to the fact that the latter was only introduced somewhere around the story's climax, and the former had spent a large portion of his time pining after Jean. The game's justification is that the epilogue takes place after a Cosmic Retcon, and the two probably had a more developed romance in the new continuity that the protagonist knew nothing about.
- In Fire Emblem Awakening characters form friendly/romantic bonds by fighting side by side. The protagonist Chrom is in a special case because the plot will force him to be married by end of the eleventh main story-related battle no matter what. If the player didn't already marry him off at that point, the game will automatically give him a wife. Olivia becomes an available combatant during the very battle at the end of which he has to be married, in contrast to the 3-4 note other candidates with whom a proper romance is possible. That battle is Chrom's only chance to befriend Olivia before his wedding and they need to fight side by side a minimum number of times to get married, making them a very narrowly averted case of this trope note . There is however a straight case in the game: if Chrom can marry neither Olivia nor the "proper romance" candidates, the mother of his baby daughter after the two-year Time Skip will be a Satellite Love Interest simply known as "Maiden" depicted with a generic female villager portrait and with literally no other role in the story. Dialogue will imply that Chrom met, romanced and married her, all during the Time Skip.
- A few of these slip by in Homestuck's many timeskips.
- The audience first learns that Jade and Davesprite were dating when she announces their breakup.
- Another example is Gamzee and Terezi's abusive black romance, which the audience very rarely gets to see play out on screen, with most of its coverage until the very end of the relationship and timeline consisting of the negative effects that it's having on Terezi and the other characters reacting to it.
- Another couple, Dave and Karkat, had this work against them, as the audience can see they got much closer during the Retcon timeline but how and why is left so vague that the relationship's nature and quadrant (and whether they were Strangled by the Red String) is a major point of fandom debate.
- Dark Star and Phala of L's Empire had no hint of attraction to one another when they met. Cue two weeks later, and they had a son off-screen (the mechanics behind the conception and fast pregnancy were Handwaved with "we were drunk at the time").
- Stand Still, Stay Silent has a Just Before the End sequence that focuses on various people that would go on to be the ancestors of the main characters introduced 90 years later. A couple of the sequences cause this:
- The main characters of the Norway sequence are a group of four friends made of two men and two women. Neither of them seem romantically involved with each other. The descendant of one of the pairs has her great-grandmother's first name, which is the only in-story hint of how these friends ended up pairing up aside from two easy to miss portraits seen in a flash-back.
- The Denmark sequence has the members of a future couple meeting for the first time. The man has family in the area in which they end up stuck because of the disaster. Before we see their descendant, the only hint of the two of them going somewhere romantically is a Time Skip photo that shows that the woman is staying with the man's family.
- Beckett, Reversal's best friend in Roll To Breathe is suddenly seen with a date to the Spring Fling. Said date is Prism, known metahuman delinquent and a member of a rival group to the Final Hazard. The two are then referred to as boyfriend and girlfriend, with no explanation as to how or why they are dating.