Most Western cultures expect that a marriage proposal is preceded by some form of courtship period. Fiction generally reflects this, with most Relationship Upgrades occurring via the characters involved switching from platonic friends to dating each other.
However, some characters have known each other long enough that any courtship would be redundant. After all, good friends who have been close for a long time—in many cases, since they were children—presumably know pretty much all there is to know about their prospective partner. So, when they finally realize (or acknowledge) that there is Unresolved Sexual Tension between them, it ends up resolved by an on-the-spot marriage proposal.
Compare to First Girl After All and Fallback Marriage Pact. A Childhood Marriage Promise might involve this if the two actually end up together. Contrast with Fourth Date Marriage (when characters have only just met and get married) and I Don't Want to Ruin Our Friendship and Better as Friends (when one or both prefer friendship to romance).
- Defied in The Son's Veto. The protagonist is a widow, who wants to marry her Unlucky Childhood Friend (having married her first husband because she didn't dare refuse), but can't because her son doesn't want a commoner as a step-father.
- Emma: When Emma and Mr. Knightly realize that they love each other they get engaged with no formal courtship. They don't really need one, though, because they've been the best of friends for most of a decade by that point.
- This is mixed with Pair the Spares in the end of the first Arcia Chronicles duology. Shander Gardani is a former palace guard captain who is elected by the people as their new king, while Illana Yambor is a Fallen Princess, daughter of the previous king. They have both just lost the woman and the man, respectively, whom they loved, but he needs a family to start a dynasty, while she is about to be Locked Away in a Monastery, so he asks her to marry him instead, if only because they've always been on good terms with each other before. It turns out to be a Perfectly Arranged Marriage, however.
- Honor Harrington: Honor Harrington and Hamish Alexander. When they finally did fall in love, after a long professional relationship, they were foolish enough to believe that they were actually managing to hide it.
- In The Cosmic Computer by H. Beam Piper, Conn Maxwell and Sylvie Jacquemont were just friends for half the book until they suddenly decided to get married at the end.
- Boq tries to invoke this in Wicked by offering to be friends with his crush Galinda and work up from there. It doesn't work.
- The White Queen: Because they are Childhood Friends imbued with Puppy Love, Richard of Gloucester and Anne Neville's burgeoning romance requires merely four encounters (once at the Battle of Tewkesbury, once at a hunting gathering, and twice in a garden) before he pops the question, which she eagerly accepts.
- Half of the couples in The Drowsy Chaperone: Underling has been Mrs. Tottendale's butler since Mr. Tottendale was alive, and it's implied that Kitty has been a problem performer for Feldzieg for a while. Regardless, the pairs end up married by the end of the show.
- The default in Harvest Moon. Some games have dates (anywhere from a few festivals a year to more formal ones), but for the most part courting consists of giving your love interest presents, seeing their heart events, then proposing.
- In Fire Emblem the support system requires a pair of characters to carry on a thread of three or four related conversations before they declare their love for one another. It's implied that they talk more than three times and these are the only conversations the player gets to hear. And occasionally its implied that they start dating after the final conversation and then are married sometime later in the epilogue. However in Awakening, by conversation four someone actually pops the question, engagement ring in hand.
- In most BioWare games, initiating a Romance Sidequest usually requires first building up the Relationship Values (i.e. becoming friends with) with the potential love interest, or at least hitting several Event Flags to the same effect.
- Varrick and Zhu Li from The Legend of Korra have been working together for years but their relationship was always on a platonic, professional level. Zhu Li eventually gets sick of feeling like a Beleaguered Assistant who isn't treated as Varrick's equal, but right before they go into a dangerous battle Varrick proposes to her. They get married afterwards.