Mecha Bowser

Mecha Bowser, also known as Bowser (Mechanical), Mechanical Bowser, or Stone Bowser, is a giant robotic statue of Bowser's upper half. It appears primarily in Bowser's Castle in the Mario Kart series, and spews fiery projectiles in every known appearance. A very similar entity is the Bowser Monument of Mario Kart 8.

Mario Kart: Double Dash!!
Mechanical Bowser debuts in Mario Kart: Double Dash!!, appearing towards the end of Bowser's Castle. It slides horizontally along a rail next to a hairpin turn along the top of a castle wall where the track is, shooting large fireballs. These fireballs move at high speed through at a single height and can prove dangerous to racers racing both towards and away from the colossal robot; particularly those attempting to perform the shortcut skipping over the hairpin, where spinning out may result in failing to make the jump and falling. It moves in a very jerky, mechanical manner.

Mario Kart Wii
In Mario Kart Wii, Mecha Bowser appears in the Bowser's Castle course. Its model looks almost exactly the same, though its movement is far more fluid and organic. It overlooks the end of a long stretch in the center of the track, halfway through the course, now seemingly coming out of the lava. As racers drive towards it, it launches large fireballs which bounce along the the middle of the track until they explode, acting as a hazard which adds a major risk factor to taking the middle - and fastest - route through the room. The racers then drive past Mecha Bowser on either side of it, as the track splits into two when it reaches the robotic Koopa.

The fireballs Mecha Bowser launches in this game have a unique look, appearing to have a hole-covered sphere inside of them that gives them a glowing polka-dotted appearance - the Mario Kart Wii game guide refers to them as molten cannonballs, which would explain their explosive properties, particularly comparing them to the cannonballs launched by the Shy Guy Galleon on GBA Shy Guy Beach.

New Super Mario Bros.
In New Super Mario Bros., in the Danger, Bob-omb! Danger! minigame, a Mechanical Bowser is the primary obstacle. It moves around, shooting fire in an attempt to light a Bob-omb Buddy. Using the stylus, the player must help the Bob-omb escape from the fire. Likely due to it being a sprite instead of a model, it has a more stony appearance.

Profiles

 * Mario Kart Wii game guide: "This massive mechanical monster throws out a molten cannonball that stops and spins you out. Dodge it to remain on course!"