Usually the run ends by going fast and completely ignoring the game's final boss, which can be a bit anti-climactic. But just this once, Charbunny is willing to fight him.
In the final level with Yoshi (18-6), we can either bring him with us to the flagpole and triumphantly ride him into the castle (slow), or we can drop him into the depths of a bottomless pit to die in a classic Mario maneuver (fast)