Someone had way too much fun writing that article. Witness "This allowed them to model how a giant impactor, perhaps one to three times the mass of Earth, would have deposited “material and energy inside Uranus” and how much debris would be left over, from which moons could form."
On the serious note without the joking, Uranus spins on it's axis tilted almost 90 degrees. In other words sometimes it faces us with it's pole, (north or south) facing the earth. Latest theory is that yes something massive smashed into it early in it's formative years. And i now wish I could think of a joke but I can't, O well!