Yfful
The opposite of luffy. The legendary enemies of planet earth who utter ancient curses and create powdered smoke from fire itself. If you see a Yfful, do not run away. They are misunderstood creatures, prone to anger issues, and have problems sitting still. They look like regular people, but if you make them mad you might end up dead.
"I'm pretty sure Ellen's a Yfful."
"Don't make her mad or she'll kill you!"
"Don't make her mad or she'll kill you!"