Needs More Examples. Desperately. Rolling Updates.

Mostly an anime trope. When Alice and Bob both Cannot Spit It Out or have had an Unresolved Sexual Tension for a long time, it's not rare that fate helps a little by making one of them trip for some reason (often a fight) and fall on the other. In some cases, they will separate and apologize, or Alice will scream and slap Bob, calling him a pervert.

But if this trope is in action, neither will happen. By the magic of the position they fell into, they will look intensely into each other's eyes and their lips will slowly get closer, before locking into a True Loves Kiss. If there is no immediate kiss, it will at least be a Aw Look They Really Do Love Each Other moment.

Compare Crash Into Hello, which has little chance to result in a kiss for obvious reasons.

A Sister Trope to the less romantic and more comic Suggestive Collision, which can result in Marshmallow Hell or Thanks For The Mammary but is much less likely to end well. Compare Meet Cute, which introduces a future relationship between two characters. Also see the logical conclusion, Official Couple.

Examples:

Anime And Manga:

• This happens to Erza and Jellal in Fairy Tail. Although it's unclear whether they actually kissed or not, it's the first time they express their mutual love so clearly.

Literature:

• In The 39 Clues, Ian Kabra rescues Amy Cahill and, in the process, somehow falls on top of her. This is quickly followed by a kiss, although the Relationship Upgrade doesn't last long.

Live Action TV:

• During Buffy The Vampire Slayer's amnesia episode, "Tabula Rasa", Willow and Tara fall on each other and share a moment.

Western Animation:

• Lion King does this during the "Can You Feel The Love Tonight" montage with Simba and Nala tumbling down a hill.