Swiggler

Swiggler is a large, Shroob-created, bio-mechanical Wiggler that is vital to the Shroob's conquest of the Mushroom Kingdom. Swiggler has the unique ability to transform the vim sucked from Toads into a fuel source for the Shroob's flying saucers. The giant Wiggler resides in a special room in the Vim Factory. In his lair, Swiggler will drink vim and use special chemicals inside its body, transforming the vim into fuel. Shroob UFOs will then attach themselves to Swiggler with special conducts, powering up the flying saucers.

During the events of Mario & Luigi: Partners in Time, Mario, Luigi, Baby Mario, and Baby Luigi confront the massive Swiggler inside the Vim Factory. In battle, Swiggler can shoot poisonous clouds at the brothers (which can be countered with Hammer strikes, although some requires two hits). Swiggler also has a glass of green Vim, which it will drink and power-up nearby Shroob UFOs. This allows the flying saucers to shoot energy blasts at Mario and Luigi. Fortunately, the heroic brothers can jump over these blasts to avoid damage. The left one will shoot at Mario and the right one will shoot at Luigi, however they can swap places and attack different brothers.

Attacking Swiggler proves to be relatively useless, as the monster has extremely high defense and will always counterattack the Mario quartet with several shockwaves immediately afterwards, forcing the heroes to jump to avoid them. This attack comes in addition to Swiggler's regular attacks that comes in on its turn.

During the fight, Swiggler is aided by two Dr. Shroob guards. If one is destroyed, another Dr. Shroob will appear to take its place. The Dr. Shroobs behave exactly as they always had prior to the quartet's encounter with Swiggler: they will use red and gray Shroob mushrooms to grow and shrink, respectively, attacking once they assume the new form. These Dr. Shroobs unintentionally aid in Swiggler's demise. This is because, by attacking them, the heroes can knock the Shroob mushrooms usable by the Dr. Shroobs into Swiggler's Vim drink. If a gray Shroob mushroom is knocked in, Swiggler will grow sickly and be weak upon drinking it, lowering its defense, and making it unable to attack. This presents a perfect opportunity for attack. Regardless, Swiggler will always return to normal after a few turns. On the other hand, if a red mushroom is knocked in, the solution will heal Swiggler significantly.

After the long battle, the Mario Bros. counterparts emerge victorious. The vim-transforming monster is destroyed, and a Cobalt Star shard is discovered. However, the victory ends as a partial loss. In the end, Baby Bowser arrives and steals the Cobalt Shard, also the one the heroes got at Baby Bowser's Castle. He escaped in his Koopa Clown Car to Yoshi's Island.

Trivia

 * Swiggler's name is a portmanteau of the word "Wiggler" and the word "swig," a small sip.
 * During the battle, the four Mario Bros. will be awarded Experience Points and Coins for every Dr. Shroob that is defeated, meaning the player can delay the end of the fight to boost their coffers and maximize their EXP.