Neptune was the first planet to have its existence predicted by mathematical calculations before it was seen through a telescope. According to Space, wind speeds on Neptune can reach up to 1,500 miles per hour; the fastest detected in the solar system as of 2014. This incredibly high wind speed was recorded by Voyager 2 in 1989 and was linked to a storm larger than planet Earth.
Neptune has a wildly fluctuating magnetic field, as the planet's magnetic poles are shifted over by roughly 47 degrees compared with the poles on which it spins. Neptune is also the coldest planet in the solar system, with temperatures in the upper atmosphere dipping down to minus 221 degrees Celsius, not surprising for a planet 2.8 billion miles away from the Sun.
Another interesting fact, detailed by Universetoday, is that Neptune's largest moon, Triton, has a retrograde orbit, meaning it orbits around the planet in the opposite direction of the other moons. Scientists speculate this is likely because Neptune captured Triton as it was going by, not forming in place as did the other satellites. Also, because of the retrograde orbit, Triton is falling inward toward the planet, eventually to be torn apart by the planet's gravity.