I looked up the figures a few days ago - but having since driven to the other end of the country, I've forgotten the precise details. IIRC it was something like Goofy having a higher aphelion - so most of the time (and length of orbital arc) it is going to be further out than Pluto (by a few %, but it also has higher eccentricity, so it's aphelion is lower than Pluto's (and indeed, Neptune's ; which is also true for Pluto). Since orbiting objects travel faster at aphelion than perihelion, that makes the average orbital period of Pluto and Goofy the same (or their year the same, or their semi-major axis the same ; these all mean the same thing) despite Goofy travelling further per orbit than Pluto, with a faster arc near perihelion.
You see the same sort of thing with, say, Uranus, Neptune, and 1P/Halley ; Halley and Uranus have quite similar orbital periods, but Halley's aphelion is well out beyond Neptune's orbit. the long period it spends out there is counterbalanced by the 3 year long Sun-dive it does form (approximately) Saturn's orbit, to the Sun, and back out to Saturn's orbit.50-odd% of it's orbital path followed in about 5% of it's orbital period.
Just because Newton's laws are quite simple, doesn't mean that their consequences are simple. Just ask (if you can get his bones to talk) one J. Kepler, who had to work out the orbits from raw observational data, unsullied by Newton's theoretical framework.
(It still sometimes astonishes me that there is no simple way to calculate the length of an arc of an ellipse or it's total perimeter - you have to do a really complicated, progressive approximation calculation for each specific shape of ellipse. Which, when you realise that Kepler would have had to make hundreds (thousands?) of such approximations while reducing Brahe's data, explains why Kepler came up with at least one relatively good approximation to the length of an ellipse's perimeter.)