"She always did love to dance."
— Simon (about River), Serenity
"A warrior who cannot dance? Clumsy in both war and peace he is."
"My life may end in a big song and dance number."
— Parson (when being attacked by an army of these), Erfworld
"I'm told I can cut a rug, but tonight it's gonna bleed."
— The Megas, "Can't Stop The Top"
It's the method of travel for little girls; how bad could it hurt? Well, without getting too deep into the physics of it, Ebersole uses the centrifugal force of the cartwheel to pull all nearby happiness to the center of his body. This leaves his feet with nothing to feel but hate.