Instant Seiza

A common outcome of a Crash Into Hello involves both parties lying on the floor stacked one on top of the other, in the same position they'd be in if they were extremely passionate about one another.

After a beat, the two will instantly teleport to a seiza position, facing away from one another and blushing furiously. If they can talk to one another, they'll either stammer furiously, or one will berate the other.

Anime and Manga

 * Skip Beat!: Kyouko is prone to doing this, though does it more because she's truly sorry for something. Interestingly enough, she seems to do this to Ren quite often.
 * Mahoraba: Both Kozue and Shiratori are very prone to this.
 * Love Hina: most notably when Naru and Keitaro are hitchhiking with Mutsumi while escorting her home, riding in the back of a truck.
 * Ranma ½
 * Kashimashi: Girl Meets Girl
 * Subversion: Keiko in Tenshi na Konamaiki takes advantage of being pinned under Fujiki to scream and accuse him of being a pervert, in order to knock Megumi down a peg.
 * Played with in FLCL, where Haruko goes into Instant Seiza after hitting Naota, then starts rolling and moving around jerkily... while still seated in the seiza position.
 * Occurs in Zone of the Enders: Delores, i... between two sentient Humongous Mecha, after a bump puts one's head in the other's lap.
 * An innuendo-free version occurs in Azumanga Daioh, when Chiyo walks in on Sakaki playing with her cat Maaya. Nothing naughty, just... undignified.
 * Erio and Caro do one after their Crash Into Hello in Magical Girl Lyrical Nanoha StrikerS, though they were facing each other and only Erio was blushing and stammering, and even then for just a few seconds. It seems the kids are too young to be fully affected by the embarrassing situation.

Web Comics

 * Narrowly averted in Ears for Elves, where Rolan (who floored Tanna when running) gets up too quickly for Tanna to protest/push him off/berate him. Therefore, there isn't a sezia but there would have been if he had stayed a moment longer.