Sometimes stylized as "run up, get done up". It is a warning given out to those that seem to be contemplating making a violent move against a person or group.
Run up, in this situation, is referring to someone "running up" on another person with the intention of fighting or jumping said person.
In the given context, Done up refers to someone being on the receiving end of a beating.
To put it simply, it means "You can run up on me and try to attack me if you would like, but if you do I'm going to kick your ass."
Ruler of Lake Titicaca. Rumored to have a bunghole that gets very angry if it does not receive toilet paper. Cornholio the Great is often seen walking around with his shirt over his head and his hands in the air, chanting songs about his power, and his bunghole.
"I am Cornholio! You do not want to face the wrath of my bunghole, for I need TP!"
Butthead: Shut up, Beavis! (uh huh huh huh)
Beavis: Um, okay. (heh heh heh heh).