Isaac Newton was a very interesting person. He was extremely introverted for most of his life. At times he could be extremely passionate and sometimes even violent. It was reported by Newtons colleagues that he only ever laughed one time and his laugh was a sarcastic one not even a sincere laugh. Many psychologists believe that Newton behaved this way due to his treatment during his childhood.
Newton vs Hooke
Robert Hooke was a very brilliant scientist but he fell under Newtons shadow. Dispute between Hooke and Newton originated from a paper that Newton published. The paper came under fire because of ungrounded claims that Newton had plagiarized Hooke. Subsequently Newton went into hiding and focused all of his energy on his studies. In 1679 Hooke and Newton exchanged letters and began discussion of planetary motion. Quite suddenly Newton cut off correspondence with Hooke. It is believed that this discussion is what lead Newton to some of his great breakthroughs in mechanics. In 1687 Newton published the first two books of the "Principia". Soon after Hooke was publicly claiming that he deserved credit in Newton's books as some of the theory was due to his help. This angered Newton so much that he threatened to not publish the final book of "Principia". Eventually he gave in and sent the third book to the presses. Newton disliked Hooke so much that he waited till Hooke's death in 1803 to publish his book "Opticks".