Monke brain is when you do something instinctively, without thinking. Usually happens when something rare appears.
Jerome: Iâm sorry that I went monke brain on you.
Alex: YOU KNEW I WANTED THAT SHINY MOLTRESS YOU ASSHOLE
This is the lowest point a human can go to. Beyond this, you arenât even a human anymore. Used as a laugh that scares many.
Katy: MICHAEL! HOW COULD YOU KILL 30 PEOPLE IN COLD BLOOD?
Michael: hehehahaha