A chimpanzee crawled up to the smokestack
Destroyer pulled into a foreign port, and put down maximum liberty. The skeleton crew didn't notice a chimpanzee, escaped from a nearby civilian transport, crawled up the ropes and up to the smokestack.
Down the stack, it made its way into the engine room. It came across a power panel opened up for maintenance, couldn't read the warning signs, and with a bright blue blast shorted out the ship's electrical system, and plunged the ship into darkness.
A little bit later, two junior Hull Technicians wander down with their flashlights, looking for the problem. They come upon the blackened body of the chimp. They shine their flashlights on its long, burnt arms. They look at each other. They highlight its short legs and odd feet. They look at each other.
Finally one says, "Well, it's too hairy to be an Electrician, the legs are too short for a Hull Tech, and there would be more tatoos on a Bo'su n. Call the wardroom, see if one of the duty officers is missing."