Yoob's Belly is a location that appears in Mario & Luigi: Partners in Time. During the events of the game, Mario, Luigi, and their young counterparts find Kamek and Baby Bowser on Yoshi's Island mountaintop, possessing the two Cobalt Star Shards they need. After the protagonists beat Kamek, they start pursuing Baby Bowser, who had ran off. Luckily, he is cornered by a dead end and the Mario Bros. catch up with him. But while trying to get the Cobalt Shards (which Baby Bowser had eaten for revenge of Baby Mario and Baby Luigi eating his Yoshi Cookies), they are noticed spotted by some Shroob U.F.O.s. They fly over to the side of the mountain and make Yoob (who was climbing up the mountain) humongous, more than he already was.
Yoob is now big enough to see the group, and proceeds to eat the two Marios and Luigis and Baby Bowser. Now inside the significantly enlarged monster, Mario, Luigi, Baby Mario, and Baby Luigi must find a way out, and while doing so they find a Green Yoshi trying to push a heavy Chomp Rock into a hole, widening a small passage inside of Yoob that will allow them to continue. After confronting the Yoshi, they are given the task to rescue and save a few other Yoshis around the place, and they manage to shove the Chomp Rock into the hole and clear out the tightened passage. The Mario Brothers then proceed to find a way out of Yoob.
Eventually, the protagonists discover that Yoob also has a bio - engineered factory inside himself, trapping Yoshis into Yoob eggs. They will soon transform into small Yoobs if they aren't freed in time. Mario, Luigi, and the babies soon meet a blue Toad named Toadbert, one of the passengers of the time travel expedition with Princess Peach and Toadiko. He claims he can't remember a single thing about what happened to her, although he had a stained map of Peach and Princess Shroob's battle.
The group finally approach the exit, though they find Sunnycide blocking the path out and protecting the Yoob eggs. He throws an egg at Luigi, cracking open and revealing to be Baby Bowser. After beating the monstrosity, the passage opens and the Yoshis, Toadbert, Baby Bowser, and the Mario Bros. escape and land back onto Yoshi's Island. Meanwhile, Yoob, having his source of energy gone, "deactivates" and falls to the ground unconscious. The group may go back into Yoob's stomach anytime they like in the game.
- Dry Bones
- R.C. Shroober
- Sunnycide (boss)