The English mathematician John Wallis (1616-1703) was a friend of Newton. According to his diary, Newton once bragged to Wallis about his little dog Diamond.
“My dog Diamond knows some mathematics. Today he proved two theorems before lunch.”
“Your dog must be a genius,” said Wallis.
“Oh I wouldn't go that far,” replied Newton. "The first theorem had an error and the second had a
pathological exception.”