Yoob

Yoob is a giant Yoshi-like creature created by the Shroobs that appears in Mario & Luigi: Partners in Time. He starts out as a large magenta and green egg, where it becomes an attraction that tourists can see for five coins. When Yoob hatches from the egg, he eats the Yoshis.

Mario & Luigi: Partners in Time
Yoob is first seen after discovering a group of Yoshis still hiding on Yoshi's Island. He quickly eats all of them, including Yoshi and Kylie Koopa, although Kylie is quickly spat out. Yoob then leaves the area, though he is later seen eating Kamek after the quartet find him on the island. After the adult and baby Mario Bros. beat Kamek and they corner Baby Bowser at the cliff, Yoob climbs to where they are, and two Shroob saucers appear and enlarge him. Yoob then proceeds to eat Baby Bowser, Mario, Luigi, Baby Mario, and Baby Luigi.

Once inside Yoob's Belly, the group (sans Baby Bowser) helps some of the previously swallowed Yoshis move forward in Yoob's stomach by pushing a Chomp Rock, which clears a path that lets them walk through Yoob's intestines. They then discover that part of Yoob's belly is a factory for trapping Yoshis. The factory, maintained by RC Shroobers, stores Yoshis in eggs, then places them on a conveyor belt that takes them to Sunnycide. The group helps the Yoshis push the Chomp Rock away, then find Toadbert, who has forgotten everything that happened after he traveled back in time, but is still taking care of some trapped Yoshis. Toadbert tells them that Sunnycide is guarding the exit, and they go to confront it at the end of Yoob's belly. Sunnycide uses the eggs in battle, and likewise, the heroes can free the Yoshis by breaking the eggs. Eventually, they defeat Sunnycide, and everyone, including the Yoshis, Toadbert, and Baby Bowser, escapes Yoob through the digestive tract, while Yoob stops functioning altogether.

If Mario and Luigi return to Yoshi's Island, they can find Yoob's inactive body still on the cliffside. They are able to re-enter Yoob as they wish, though they must exit through the digestive tract again.

Super Mario-kun
In the Super Mario-kun, Yoob appears in volume 36. Unlike in Mario & Luigi: Partners in Time, Yoob originally was just a giant, carefree, friendly Yoshi who is gluttonous. He is used as a vessel for Sunnycide, as Sunnycide takes control of the giant Yoshi and turns him into a Yoob. After the brothers get eaten, they defeat Sunnycide inside, which reverts the Yoob to his normal state. The giant Yoshi then eats the Cobalt Star Shards, which causes the brothers to panic, and ends the chapter. They manage to get the shards out of him.

Appearance
Yoob resembles a magenta Yoshi, except he is much larger and fatter (even bigger when the Shroobs zap it), has black spines, a black saddle, blue shoes, green underbelly, black irises, red pupils, and pincers. Yoob bears a loose resemblance to, the host of the educational children's programs ' and '. As a matter of fact, a Nintendo Power issue predating the release of Mario and Luigi: Partners in Time mentioned the similarities in a pre-release screenshot of the game.

Trivia

 * When the babies dig underground or attack with the hammer inside Yoob's Belly, Yoob can be seen suffering in pain on the top screen. He also suffers when the babies open a part in his belly using the buttons and when the Yoshis roll the Chomp Rock down his stomach, creating a path. This stops after Sunnycide is defeated.
 * In Mario & Luigi: Bowser's Inside Story, an enemy named Fawful Guy has an attack where it is eaten and turned into an egg by an off-screen creature, which roars in an identical manner to Yoob's. The game's remake does not retain the roar however.

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