Imagine your OTP as teenagers at person A’s house having a sleepover. They are having a pillow fight and A swings their pillow back to hit B with it… and breaks a lamp, bringing the pillow fight to an abrupt halt, as A panics about getting in trouble.
OT3 version: A swings their pillow to hit B, and ends up hitting C and knocking them over. A and B immediately check to make sure C isn’t hurt.