Such event might only happen once every hundered million years or so! Why? This is because Regulus is a star(it is really not, it is probably a eclipsing binary system. It orbits the the galactic center of the Milky Way which takes probably less than 230 million years(How long it takes the Sun to orbit the galalctic center of the Milky Way) or more. It depends Where Regulus is located in the Milky Way.
Facts about planets in the sky:
Venus is the brightest object in the sky. Mars is the red-looking star. It has this retrograde motion because of Earth and Mars in their orbit around the Sun