Toothed whale brain size with the expected brain size based on such allometric analysis provides an encephalisation quotient that can be used as another indication of animal intelligence. Sperm whales have the largest brain mass of any animal on earth, averaging and in mature males, in comparison to the average human brain which averages in mature males. The brain to body mass ratio in some odontocetes, such as belugas and narwhals, is second only to humans. Dolphins are known to engage in complex play behaviour, which includes such things as producing stable underwater toroidal air-core vortex rings or "bubble rings". Two main
The Day the Earth Stood Stupid into "Pride and Prejudice". Fry breaks free of the illusion, and quickly writes a story in which he is crushed to death by a bookcase, one riddled with "plot holes and spelling errors". In accordance with the story, the giant brain announces it is leaving Earth "for no raisin" (Fry's misspelling of "reason"), and the people of Earth regain their intelligence. Other than the Nibblonians, Fry is the only other one to have any recollection of the event, and no one believes his story. Nibbler returns to his undercover position observing Earth as Leela's adorable pet. Fry's immunity to the