Originating from the hypothetical of "IF I SHOOT TWO DOGS IN THE FUCKING FACE, IT DOESN'T MEAN I CAN NOW SHOOT A THIRD DOG BECAUSE I SHOT TWO DOGS ALREADY" (which it in itself is a comedical way of saying "Just because you do something bad to other people doesn't make what you're doing now any less bad.") , shooting a fourth dog is when someone's rhetorical/ethical/or hypothetical question is made fun of or insulted and them responding with a hyper-exaggerated Babyrage.
Thimble: "Hey that presentation about ducks was pretty good..... NOT! IT SUCKED LMAO NERD."
Jumple: You abhorrent scum. You ignorant fool. I will sue you. You are going to be the target of the greatest lawsuit the world has ever seen. You don't know why? It's completely obvious. It's so obvious, the most deplorable peasant could grasp the full magnitude of your wickedness and treachery with the greatest of ease. Your actions cry out for mercy, and I will be happy to deliver it. And if you're thinking this is a mistake, or merely a deception of mine, you're sadly mistaken, my friend. I have indisputable proof of your continued harassment and other offenses. Even without it, the jury would take one look at you and decide. The incomprehensible magnitude of your crimes brings with it unavoidable, infinite guilt, and whether you notice it or not, everyone else does. Are you interested in who will be serving as the offense attorney? I'll tell you. It's my father. Your defense? It doesn't matter, in fact, they might just not give you one even to spare just one individual from the trauma. My father is the greatest lawyer in the US, the world, and human history, including the future, which he knows due to the fact that he sued the future and they travelled back in time to-"
Thimble: "...... Jesus H Christ you really shooting a fourth dog with that one....."