Nightmare of Baldimore

The Nightmare of Barujimoa (バルジモアの悪夢) was an incident that occured when a large portion of Karakuri Island was blown up by an explosion caused by Franky, who activated the self-destruct switch in Vegapunk's Lab. Although Kitton's grandfather warned him about it, Franky mistook the button's skull and crossbones design as a pirate symbol and pressed it, causing the whole lab to explode. News of the incident soon spread around the world and was dubbed "The Nightmare of Barujimoa".

Trivia

 * This is the second time a "danger" skull and crossbones was mistaken for a jolly roger, the first being when Chopper went to look for the poisonous Amiudake mushroom. Interestingly, both instances involved a doctor of one profession or another.