Gobblegut

Gobblegut is a boss in Super Mario Galaxy 2. He is a dragon, who encircles a small planet in Bowser Jr.'s Fiery Flotilla, burrowing into and emerging out of it, in the mission Gobblegut's Aching Belly.

Appearance
Gobblegut resembles a giant serpentine dragon with a row of numerous red ulcers growing from his body. His scales have beautiful swirl designs and his underside lacks any scales thus exposing his pink skin. Gobblegut has a few jagged rocks protruding from his head, and he has a large bulbous chin that has numerous scars on it (most likely due to the numerous times he slams his chin into solid rock).

After becoming Fire Gobblegut, his scales change from light green to lava red, and his skin changes to orange. He also releases lava and fire from his skin and the stones on his body have become orange. However, his ulcers remain unchanged.

Strategy
The giant dragon circles the planet and eventually swoops down and crunches down on the surface of the planet in an attempt to injure Mario. When he blows his train whistle he dives down and tunnels right through the middle of the planet thus, exposing his bellyache bulges. The six bulges surrounding Gobblegut's body can be damaged when Mario uses a spinning attack when they get temporarily stuck in the planets surface while tunneling. After three hits, Gobblegut becomes angrier and starts moving faster. After the last bellyache bulge gets damaged, Gobblegut slows down, burps, and finally explodes, releasing a Grand Star.

The player faces Gobblegut twice, with the second fight being under the Speedy Comet conditions.

Fiery Gobblegut is fought in the same way with some differences. One of them is that burns Mario on contact. Also, after three hits when he crunches into the planet's surface he leaves lava pools. The plumber must avoid those lava pits that remain throughout the battle and not to be burnt by the fireballs that Fiery Gobblegut spits often.

Fire Gobblegut
A fire version of Gobblegut is fought as a secret boss at the Battle Belt Galaxy. This Gobblegut is much tougher, as he'll leave behind lava pools when biting into the battlefield. He'll also spit fireballs at times to make it harder for the player.

Trivia

 * The Wiggler boss in Super Mario Sunshine acts similarly to Gobblegut, getting angrier and making train noises every time it gets hit.