This article is from the Final-Fantasy and other Square Soft Games FAQ, by firstname.lastname@example.org (Nick Zitzmann) with numerous contributions by others.
There are many secret characters in the game; unlocking them depends on
how many times you finish Story Mode.
Finishing it once gives you Bahamut. His special ability, Megaflare,
takes a while to charge but causes every other cart on the course to
Finishing it twice gives you Squall (from Final Fantasy VIII) and his
special ability, Gunblade.
Finishing it further will unlock some other popular Final Fantasy (and
non-Final Fantasy) characters which can be selected by highlighting
Squall and holding down another button on the controller while pressing