Shroob Rex

A Shroob Rex is a purple Shroobified Rex found in Shroob Castle, the Shroobified version of Princess Peach's Castle, during the events of Mario & Luigi: Partners in Time. These dinosaurs were used by the Shroobs to protect the castle, their base of operations on Mushroom World. The four Mario Bros. of past and present fought many Shroob Rexes during their efforts to rescue Princess Peach, defeat Princess Shroob, and eliminate the Shroob menace. Shroob Rexes never appeared in the overworld, only in battle alongside other enemies. Interestingly, normal Rexes did not appear in Mario & Luigi: Partners in Time at all.

In battle, the Shroob Rex uses a wide variety of attacks to injure the Mario Bros. First, the dinosaur may briefly fly in the air with its tiny wings, then Ground Pound the floor, creating a seismic energy wave. This attack could be dodged by jumping. However, depending on where the Shroob Rex Ground Pounds, the timing changes. If the Shroob Rex ground pounds closer to Luigi, the green-clad brother must jump first, followed by his brother Mario. If closer to Mario, the elder brother must jump first, followed by his younger brother. If the Shroob Rex Ground Pounds equal distance between the two, both Mario Bros. must jump at the same time to avoid the energy wave.

A Shroob Rex can also shoot boulders at the Mario Bros. from its mouth. These boulders are on fire and can be deflected with a Hammer strike. When shot, the boulder may split in two, requiring both Baby Mario Bros. to swing their Hammers at the same time to destroy the dangerous rocks. Additionally, the Shroob Rex may fire one boulder that homes in on one Mario Bro. When deflected, the boulder will roll into the second Mario brother, and must be deflected again. It will home in on Mario first when it lifts its head up before spitting out the fireball and it will hit Luigi first if it lifts its head down. If it doesn't lift its head at all the fireball will split in two.

The Shroob Rex's final attack is simply charging into a Mario Bro., running off the battlefield and into the back of the second Mario Bro. This attack can be dodged or countered by jumping, but only if certain prerequisites are met. This is because a normal-sized Shroob Rex is too tall to jump over. However, whenever a Shroob Rex is jumped on by a Mario Bro., it will become flatter, squatter, and shorter. Only the damaged, flattened Shroob Rex can be jumped over.