O.o
I have yet to see evidence of that such an orbit is feasible, though.
ok, let me eleborate upon my statement, sry for the absence of citation.
they generally only appear as the only celestial body in the system (apart from the star, of course), lest the other planets's gravity field will destroy it's oribt(hence, very unstable). how they tend to maintain their orbit is, when they orbit, as they approach their system's star, as it becomes closer and closer to the sun, the gravity becomes more powerful, which also allows a much smaller radius of their orbit, at the same speed. but because of the speed of the planet, this radius of orbit cannot be maintain for the full 360 degrees, and the planet is flung back into space at around 120~180 degree. but the "fling" is not enough to throw the planet out of orbit, the star's gravity slowly pulls the planet back, but at a much larger radius of orbit, thus forming a pear shape.
EDIT: FYI, i learned about this from a day at my university, swinburne.