Pluto and Triton
Pluto and Triton have the strangest orbits of all the planetary bodies in our solar system and may have some historical connection. Pluto's orbit is tilted 17-degrees and rotates the opposite direction from most other planets. It also is highly eccentric making it closer to us than Neptune is for twenty of its 249 year orbit. Triton has orbital characteristics that are equally bizarre.
Although now ruled out as unlikely, Pluto was once thought of as being a satellite of Neptune that had escaped its gravitational force and embarked on a orbit of its own. What scientists now speculate is that Pluto and Triton once moved in an independent orbit around the Sun but was later captured by Neptune. There is a possibility that Triton, Pluto and Charon are the last remaining objects that were ejected from the Oort cloud.