From the Super Mario Wiki
Bluey's Course is the second boss course in the Nintendo 64 game Diddy Kong Racing and its Nintendo DS remake, Diddy Kong Racing DS. It is part of the Snowflake Mountain zone. It is raced with the hovercraft.
Bluey the Walrus is raced twice, with the second time being much harder. The course is a snow-covered and mostly downhill area with some tunnels and giant candy canes. Giant rolling snowballs menace the entranceway to a tunnel.
In the Nintendo DS remake, the snowballs are gone and the race is much harder.