The scientist is most famous for calculated gravity, but it’s also believed that Isaac Newton invented the cat door. How Stuff Works writes that when Newton was working on his experiments at the University of Cambridge he was constantly interrupted by his cats scratching at the door. So he called the Cambridge carpenter to saw two holes in the door, one for the mother cat and one for her kittens! Apparently these holes can still be seen at the university today.
Source and Credits: purina.co.uk