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Mario & Luigi: Partners in Time
One day, an unusual egg arrives on Yoshi's Island (presumably placed on the island by the Shroobs). Although no one knew where it came from, the egg instantly became a tourist attraction. For five Coins, tourists could witness the enormous egg close-up. However, the egg soon hatched, and Yoob was released. Since Yoob was apparently wired by the Shroobs to eat Yoshis, it started terrorizing the island, eating every Yoshi in sight. The remaining Yoshis fled to safety.
When the four Mario brothers (Mario, Luigi, Baby Mario and Baby Luigi) first arrive on Yoshi's Island, the place was deserted. Most of the Yoshis had already been eaten. The few survivors were found hiding in a small tree hut. Soon, Yoob discovers the Yoshis hideout. The Yoshis attempted to flee, but Yoob eats all of them, even Yoshi. The Mario brothers survive the attack. With no more Yoshis left in the area, Yoob leaves to search for more food.
The Mario Bros. see Kamek, who says Prince Bowser is on top of the cliff and flees, taking some Yoshi cookies with him. The bros. chase him and eventually find Prince Bowser. The babies eating all his cookies, so he eats the shards he stole from the bros. and runs away. Mario and Luigi chase him and start trying to get the shards out of him when two Shroob UFOs appear and notice them. They fly off to Yoob, who is climbing the outside of the cliff, and zap him with a ray, which makes him huge, then fly away. Yoob then proceeds to eat Baby Bowser and the bros.
Once inside Yoob's Belly, the brothers discover that Yoob does not have a normal digestive system. In fact, part of Yoob's Belly is an egg factory, created by the Shroobs. The factory has Yoshis that get trapped in Yoob-like eggs on a conveyor belt which takes them to Sunnycide. It is revealed that when Yoob eats a Yoshi, the RC Shroobers in his belly handle the Yoshi. Then, the Yoshi is encased in a pink and green egg, similar to the one Yoob emerged from. This would presumably turn the Yoshis into monsters, destroying the kingdom. However, the eggs are fragile and Mario and Luigi can destroy them with their attacks and free the Yoshis, as shown in the boss battle.
Soon, the four Mario brothers put an end to the operation. To do so, the brothers aid a group of Yoshis (led by Yoshi himself) in their efforts to escape Yoob's body. By using Chomp Rocks that Yoob had eaten, the Yoshis manages to push the rolling stones through Yoob's intestines, creating a pathway for the Mario brothers to the heart of the internal factory. In the center of Yoob's stomach, the Mario brothers encounter the guardian of the Yoob eggs, Sunnycide. Sunnycide guards the exit, preventing the bros., Toadbert and the Yoshis from escaping, forcing Mario and Luigi to fight. After a long battle, the brothers defeat Sunnycide, and, with the help of a Toad named Toadbert, free the remaining trapped Yoshis. Escaping through Yoob's digestive tract, the Mario Bros. and the Baby Mario Bros., Yoshis, Toadbert (and even Baby Bowser) made it back safely to Yoshi's Island. Yoob, who needing the energy provided by the Yoob eggs to remain operational, falls asleep. All the captured Yoshis are saved before they turned into monsters.
If Mario and Luigi return to Yoshi's Island, they can find Yoob's now-deactivated body attached to the side of a cliff. In fact, the Mario brothers can actually reenter Yoob's body to find items, badges, and beans the heroes may have missed during their first time through, but will have to exit the same way they did the first time.
In the Super Mario-Kun, Yoob appears in volume 36. Unlike in Mario & Luigi: Partners in Time, Yoob originally was just a giant, carefree and friendly (albeit gluttonous) Yoshi. 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.
Yoob looks identical to a pink Yoshi, except it is much larger and fatter (even bigger when the Shroobs zap it), has black spines, a black shell, blue shoes, green underbelly, black irises, red pupils, and pincers. Yoob bears a loose resemblance to Barney the Dinosaur, the host of Barney & Friends, an educational children's program. 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.
- Mario and Luigi: Partners in Time - Nintendo DS
- 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. The off-screen creature's roar is identical to Yoob's and the egg's color is identical to the eggs Yoob creates too.
- When the babies dig underground or attack with the hammer inside of Yoob's Belly, Yoob can be seen suffering in pain on the top screen. He also suffers when the Yoshis roll the Chomp Rock down his stomach, creating a path. This stops after the Sunnycide is destroyed.