Elder Shrooboid

The Elder Shrooboid is a boss that appears in Mario & Luigi: Partners in Time. It is found in the Star Shrine and must be fought to obtain one of the Cobalt Star shards. The Elder Shrooboid has a similar appearance to the Junior Shrooboid, but is red with yellow spots and spikes on top of its head, and is the strongest of all the Shrooboids. Its name and color are a reference to it being the Junior Shrooboid's tougher, "older" lookalike, similar to how Mario is Luigi's older brother.

Prior to the encounter, the Elder Shrooboid captured Toadbert and Kylie Koopa, stealing the Toad's Cobalt Star shard. When the Mario Bros. arrive at the top of the shrine, Toadbert tries to reveal that the Cobalt Star was meant to trap Elder Princess Shroob inside, having Mario rub off the dirt on his strange sketch that he had made awhile beforehand to reveal two Princesses. He and Kylie Koopa are then turned into purple Shroob Mushrooms by the Elder Shrooboid. Hoping to gather all the shards and awaken its leader, the Elder Shrooboid then attacks the Mario Bros. and their younger selves. Defeating the Elder Shrooboid rewards the Bros. with the fifth Cobalt Star shard and access to Shroob Castle.

Battle
The Elder Shrooboid's spikes normally make it immune to any jump-based attacks and Bros. Items, and it takes critical damage from the Ice Flower. Its first attack involves trapping Mario and Luigi in crystals, similar to Shroids, and then grabbing a ball and chain. The Bros. must jump to break their crystal prisons as the Elder Shrooboid spins the ball and chain towards them. The spinning causes the Shrooboid to become dizzy, making him drop the ball and fall over; it then gets up again, screams in a rage, and angrily knocks the ball at either of the Mario Bros., while lunging head first into the other brother. Both must be dodged by jumping, and failing to break out of the crystal makes these attacks unavoidable. The metallic ball has either an "M" (for Mario) or an "L" (for Luigi) marked on it, depicting its target.

The Elder Shrooboid can also perform a spin attack similar to the Junior Shrooboid, which the baby Mario Bros. must counter with their hammers; the Elder Shrooboid continues trying to spin into the Bros. pairs repeatedly, requiring multiple counterattacks. The Elder Shrooboid can also throw fireballs much like Blazing Shroobs, and may shoot two fireballs at once; these can be dodged with well-timed jumps.

If attacked, the Elder Shrooboid will create a Spiked Ball to throw towards the Mario Bros.; the ball circles around them, moving faster with each orbit, until it closes in on one of the Bros. to strike. The ball can be deflected with the hammer, and may poison their target in addition to damaging them if it hits. Successfully timing the hammer strike sends the spiked weapon flying off into the air, causing the Elder Shrooboid to gasp and falls over from shock; in this state, it is vulnerable to jump attacks, and any attack deals more damage than usual due to its defense being lowered.

After seemingly defeating the Elder Shrooboid, it starts to shrink into nothingness, but then instantly grows to about twice its size and resumes the fight. In this state, Elder Shrooboid has the same attacks as before, but the attacks are faster and more powerful, and the objects it uses are much bigger as well. Additionally, after becoming gigantic, the Elder Shrooboid pulls a Shroob UFO from its mouth; the UFO counts down from four turns before unleashing a massive energy blast, similar to the one encountered in the scripted battle that was lost against the Shroobs near the beginning of the game. Unlike that instance, the Mario Bros. can deflect the Elder Shrooboid's spiked balls at the Shroob UFO to reset the counter and avoid an instant Game Over.

In the North American version of the game, the Shroob UFO changes position in the air during the battle, flying above either the Shrooboid or the Mario Bros.; when Baby Mario deflects a spiked ball, it flies over the Elder Shrooboid, and if Baby Luigi deflects the ball, the spiked weapon flies over the Bros., changing the character required to reset the UFO's counter. In all other versions, the spiked ball always goes up, even if Baby Mario deflects the attack. As such, the Shroob UFO stays above the Mario Bros. and is much easier to hit.

Names in other languages
Großer Shrooboid Shrooboide Rosso