Mega Man V (Game Boy) weak to specific weapon, the player is encouraged to complete some stages before others. These bosses are known in game as "Mercury", "Venus", "Mars", "Jupiter", "Saturn", "Uranus", "Neptune", and "Pluto", named after the first, second, fourth, and fifth through eighth planets in our Solar System. Pluto was, at the time the game was made, considered a planet, unlike from 2006 and onwards. Terra is named for the Latin word for Earth. Defeating some bosses will allow the player to access Mega Man's robot dog Rush, who can transform into useful "Coil" and "Jet" modes for easier stage navigation. "Mega Man
Fictional planets of the Solar System while yet others are purely fictional and were never intended as serious hypotheses about the structure of the Solar System. Vulcan was a hypothetical planet supposed to revolve around the Sun inside the orbit of Mercury, invoked to explain certain irregularities in Mercury's orbit. The planet was proposed as a hypothesis in 1859, and abandoned not later than 1915. The name "Vulcan" has been used for various other fictional planets, in and out of the Solar System, that do not correspond to the hypothetical planet Vulcan. The planet Vulcan in the "Star Trek" franchise, for instance, is specified as orbiting