2003 UB313 is a planet located further out in the solar system than planet Pluto, though it is actually slightly bigger. It has no formal name currently, simply the butt-ugly designation "UB313" (discovered in 2003). However, it has been given the nickname "Xena", due to its popularity with lesbians.
There are some who believe that 2003 UB313 should not be designated as a planet, if Pluto isn't either. And there are some who believe that instead of "Xena" 2003 UB313 should be called "Xenu".
Pluto and 2003 UB313 are technically classified as Minor or Dwarf planets, believed to be large Oort Cloud objects.