Bowser in the Dark World

Bowser in the Dark World is the first Bowser level in Super Mario 64. It is accessed on the first floor of the castle, and contains the first boss fight with Bowser.

Big Goomba
In some personalized copies of Super Mario 64, mini-bosses that take the appearance of large versions of Goombas known as Big Goombas, not to be confused with the Goombas seen in the giant version of Tiny-Huge Island, have been reported to appear in Bowser in the Dark World. They can appear on the standard path, or on an optional platform somewhat separated from the main part of the level. They can take 2-5 hits to defeat, and can drop a red coin, several coins, a power star, or some other collectible depending on the copies Big Goombas are reported in.

Stalactites
In some copies, the stage has a visible ceiling covered with stalactites, much like the skybox. Their purpose varies from being decoration to dripping water to being falling obstacles.