Pluto

Pluto is a dwarf planet and TNO.

Planet?
When it was discovered in 1930 it was classified as a planet, but in 2006 the IAU added the 3rd criteria for an object being a planet which is the object must have enough gravity to pull in other objects in the same orbit. The kuiper belt exists near pluto consisting of many asteroid-like objects, so pluto doesn't meet that 3rd criteria for being planet, so it's a dwarf planet.