On the course Sick With It, there is a glitch in the game that will actually warp you to the other side of the course. About half-way through the course, in the area with all the fallen-down trees you can grind, are two paths. One path eventually leads to an area of mogles. The other path leads to a straight-way with two small hills. The ''warp-zone'' is on the straight-way. When you're coming to the first hill, stay in the middle, but aim off to the left. Jump when you reach the top of the hill, and try to land in the snow on the mountainside. If pulled off correctly, you will fall through the mountain, then be transported to the other side of the course, in the mogles.
I know this trick can work because I've pulled it off several times already. This was in 2-player, by the way, in case that makes a difference.