Doraemon

Doraemon is sent back in time by a young boy named Sewashi Nobi to improve the circumstances of his grandfather, Nobita, so that his descendants may enjoy a better future. In the original timeline, Nobita experienced nothing but misery and misfortune manifested in the form of very poor grades and bullying throughout his life. This culminates in the burning down of a future business he sets up which leaves his family line beset with financial problems. In order to alter history and better the Nobi family's fortunes, Sewashi initially wanted to send a super-robot to protect Nobita, but with his meager allowance he could only afford an imperfectly-made factory-rejected toy: an anthropomorphic robot cat called Doraemon.