Because of Pluto's inclined orbital plane, it appears to cross paths with Neptune and will occasionally be closer to the sun than Neptune.

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Pluto's orbital plane is tilted at an angle of 17 degrees with respect to the plane of the ecliptic (the plane in which most planets orbit the Sun). This means that at certain points in its orbit, Pluto will be closer to the Sun than Neptune, which is located farther out in the Solar System. In fact, Pluto's elliptical orbit brings it inside of Neptune's orbit for about 20 years out of every 248 Earth years. During this time, Pluto is the eighth planet from the Sun, rather than the ninth.

Because of Pluto's Inclined Orbital Plane, It Appears to Cross