text: I don't think it is a planet since it doesn't have much in common with the other eight planets.  However I don't feel it is an asteriod for the same reason.  I think that the best description is a Kuiper Belt object.  These are objects located on the outer edge of the solar system that resemble large comets but never get close to the Sun.  Pluto has much in common with these objects but just happens to be one the the largest and closest.