Pluto

Pluto was the ninth planet in the Solar System, until it got demoted in 2006 by the IAU.

You may be looking for Pluto (Disney), the cartoon dog.

Origin of Name
Pluto comes from the Greek god of the underworld, but ironically, the planet Pluto is tiny in size.

Discovery
Pluto was discovered in 1930 by Clyde Tombaugh. A little nine-year-old girl suggested the name "Pluto", and that's how it got its name.

Demotion
In 2004, Haumea was discovered. It was just as small as Pluto. It was classified as a "dwarf planet". Other dwarf planets were discovered during the 2004-2006 era. In 2006, the IAU voted to demote Pluto to dwarf planet status. Ordinary citizens were outraged. For decades, Pluto had been heralded as the underdog of all planets.