Person A manages to piss Person B off. So Person A goes out to work or whatever and comes home to find their living room has been turned into a fort. There's a sign hanging on the door that says "no douche bags allowed" and Person A usually wouldn't care, but they're kind of mad at Person B, so they refuse to just let Person B have their fort and begin demanding entrance, which Person B refuses. Person A gets so mad that they break the fort, resulting in Person B attacking them with pillows. This, of course, means war. In the end, they're a giggly mess on the floor, exhausted from their pillow fight, and all is forgiven.
Except for the destruction of the pillow fort. You /know/ Person B made Person A rebuild it.