green gorilla

An unlikely scenario or chain of events. From fighting/ marital arts instruction; Instructor will demonstrate technique, a student will propose progressively unlikely "what ifs" regarding the technique, i.e. "what if he had a knife, gun, samurai sword, now there's three guys etc., prompting the instructor to say, "what if 99 green gorillas came out of nowhere and beat the tar out of you?"

The boss went all green gorilla about me being late for that meeting. He asked what if I missed a crucial detail only mentioned in the first ten minutes and it led to the company going bankrupt and all of us ending up in prison.