kaibutsu - Kaibutsu is a monster that shows up when you least expect it

Kaibutsu is a monster that shows up when you least expect it and makes your day a disaster.

I failed my science test. My friend said it was a kaibutsu from the bottom of the ocean.

My mom said my room was a kaibutsu after I didn’t clean it for a month.

My teacher said my essay was a kaibutsu because it had 10 spelling mistakes.