The extreme of going apeshit. To completely lose one'smind in a violent manner, or when used to describe a situation, the act of descending into complete chaos.
When I found out that my entire project had been deleted, I went completely apeshit bananas on everyone that had touched my computer in 24 hours.
By the time the riot police got there, everything was already apeshit bananas.
an imaginary fish from JD Salinger's short story called "A Perfect Day For Bananafish" which is found in the book 9 stories by Salinger. According to the main character of the story banana-fish are fish the swim into coral reef and holes in rocks to eat the bananas growing there but then eat too many and cannot swim back out and then die because of this.