Hop off my johnson means in a different phrase "get off my case". Used mostly when youre just joking around with your friends but can also be used when trying to get someone thats attempting (and probably failing harshly) to tell you off. They get confused, you walk out feeling good that you got away from that.
Person 1: "I bet you've nevereven been kissed before, have you?"
Person 2: "Hop off my johnson!"
*person 2 walks out while person 1 is still in a state of confusion.
The term is used when a person has loaded a Sniper and is going to shoot someone in the head. Originally meaning to elect Lyndon B. Johnson as president.
"Hey Dickhead, don't let my ass see you putting Lyndon B. Johnson into office
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).