So will Pluto and Neptune ever collide? No! You can see this in the image below, which shows a view as seen from the side as the planets orbit around the Sun. Most planets only make small excursions in the vertical and radial directions, but Pluto is an exception. Pluto at times will move closer to the Sun than Neptune, but it is always well above the orbit of Neptune when this happens. The orbits never actually cross the same point in space.
You can read more about the orbital patterns of Pluto at:
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The StarChild Team
StarChild Graphics & Music: Acknowledgments
StarChild Project Leader: Dr. Laura A. Whitlock
Responsible NASA Official: Phil Newman