Yoob

Yoob is a giant, Shroob-created Yoshi that terrorized Yoshi's Island during the events of Mario & Luigi: Partners in Time. The creature known as Yoob originally started out as an abnormally large pink and green Yoshi Egg. One day, this egg mysteriously arrived on Yoshi's Island (presumably placed on the island by the Shroobs). Although no one knew where it came from, the mysterious egg instantly became a tourist attraction. For a mere five coins, tourists could actually witness the enormous egg close-up. However, the egg soon hatched, and the monstrous Yoob was released. Since Yoob was programmed by the Shroobs to eat Yoshis, the monster started terrorizing the island, eating every Yoshi in sight.

When the four Mario brothers (Mario, Luigi, Baby Mario and Baby Luigi) first arrived on Yoshi's Island, the place was deserted. Most of the Yoshis had already been eaten. The few survivors were hiding in a small tree hut. Unfortunately, the Yoshi hideout was discovered by the massive creature. The Yoshis attempted to flee, but ultimately every last one was eaten by the massive monster. Even Yoshi, who attempted to fight the massive monster, was eaten by Yoob. Fortunately, the Mario brothers survived the attack. With no more Yoshis left in the area, Yoob left to search for more food.

Later, while climbing a cliff on during its food search, Yoob was blasted with an energy beam from a Shroob UFO. The beam caused Yoob to grow to gigantic proportions. Yoob, who was originally about ten times bigger than Mario, was now over a hundred times bigger than the heroic plumber. In fact, Mario was now smaller than one of Yoobâ€™s eyes. With an enormous appetite to fit his new body, Yoob climbed the cliff and ate the four Mario brothers and Baby Bowser (who were previously battling for control of the Cobalt Star shards).

Once inside, the brothers discovered that Yoobâ€™s stomach was not a normal digestive system. In fact, the monsterâ€™s stomach had been transformed into a bio-mechanical factory by the Shroobs themselves. The purpose of the factory was to create even more Yoobs, which could then be released against the Mushroom Kingdom. After Yoob ate a Yoshi, the dinosaur would be brought to the internal factory and tortured by RC Shroobers. Then, the Yoshi would be encased in a pink and green egg, similar to the one Yoob emerged from. In time, the eggs would hatch and another Yoob monster would be born.

Thankfully, the four Mario brothers put an end to this vile operation. To do so, the brothers aided a group of Yoshis (led by Yoshi himself) in their efforts to escape Yoobâ€™s body. By using Chomp Rocks that Yoob had eaten, the Yoshis managed to push the rolling stones through Yoobâ€™s intestines, creating a pathway for the Mario brothers to the heart of the internal factory. In the center of Yoobâ€™s stomach, the Mario brothers encountered the guardian of the Yoob eggs, Sunnycide. Sunnycide was created by the Shroobs to protect the eggs until they reached maturation and hatched into Yoobs. After a long battle, the brothers defeated Sunnycide, and, with the help of a Toad named Toadbert, freed the remaining trapped Yoshis. Escaping through Yoobâ€™s digestive tract, the Marios, Yoshis, Toadbert (and even Baby Bowser) made it back safely of Yoshiâ€™s Island. Yoob, who needed the energy provided by the Yoob eggs to survive, presumably perished without the necessary nourishment to sustain itself. Fortunately, all the captured Yoshis were saved before they turned into more Yoobs.

It is unknown if the original Yoob started out as a normal Yoshi that was then encased in a Yoob egg, or if Yoob began as a unique genetic experiment created by the Shroobs.