This is very difficult to pull off, and there are two ways to do it.
Number one (difficulty 7/10): On the platform where you start, move
ahead and fall off the right side of it. WATCH THE MAP SO YOU LAND
RIGHT ON TARGET. Bounce on the platform where the coaster ends until
you land on it. Then run into the goal. Number two (difficulty 10/10):
If you want an even more amazing replay and with a shorter time and a
higher score, drop off the starting platform, and land RIGHT IN THE
GOAL. This is extremely difficult to pull off, so don't do this unless
you're a complete daredevil and you're going for a massive score.

To save your replay to amuse your friends and family: While it is
showing the replay, hit START/PAUSE and select Save Replay. This won't
work w/o a Memory Card, though. To load your replay: At the main menu,
select OPTIONS >> REPLAY >> and then your replay.

This shortcut leads to the same goal, though :-(