DAY, THE SHROOBS WILL DANCE ON THE BURIED REMAINS OF THIS PATHETIC KINGDOM...”
—Elder Princess Shroob, Mario & Luigi: Partners in Time
Elder Princess Shroob is the true main antagonist and penultimate boss of Mario & Luigi: Partners in Time. She is the leader of the Shroobs (her younger sister is the second-in-command) , an alien race that invaded the Mushroom Kingdom. When Princess Peach, Toadiko and Toadbert came to Princess Peach's Castle of the past, they met the Shroobs. Elder Princess Shroob attempted to attack Peach; however, Peach used the power of the Time Machine, the Cobalt Star, to trap the Elder Princess Shroob inside. Peach then shattered the Star into pieces; however, the younger Princess Shroob still was able to capture Peach and trap her in Shroob Castle.
Mario & Luigi: Partners in Time EditThroughout the game, Mario, Luigi, Baby Mario and Baby Luigi collect the
various pieces of the Cobalt Star, not knowing that Elder Princess Shroob is actually trapped inside. When the brothers get to the top of Star Hill, the "spirit of the Cobalt Star" - actually Elder Princess Shroob in a disguise - appears and speaks to the brothers. It seemed that only Baby Luigi knew, since he was crying when "the spirit of the Cobalt Star" appeared. Various other characters such as Baby Luigi Kylie Koopa and Toadbert hinted the fact that she was hiding inside the Cobalt Star.
Finally, at the end of the game, after Princess Shroob is defeated, it is revealed that Princess Peach kept the center shard of the Cobalt Star. Peach tells the Mario Bros. that she cannot allow them to repair the Cobalt Star, but before she can explain why Baby Bowser comes in and steals the last shard, combining it with the five that the heroes had already collected; the Shroob Princess, now enraged over the recent death of her younger sister, turns Baby Bowser into a Shroob Mushroom and resumes her original form as Peach explains to the Mario Bros. what had really happened when she had gone back to that time period. Upon resuming her original form, Elder Princess Shroob promises to kill the Bros. as revenge for her sister's death and then activates the platform they were standing on, engaging them in battle high above Shroob castle.
Elder Princess Shroob is much stronger than her sister, and commands a fleet of Shroob UFOs. Her attacks depend on how many saucers are present; with just one, she can heal herself with a drink that recovers 120 of her HP, (80 in the Japanese and European versions) or summon a Shroobified enemy called a Shroob Chomp to attack Mario or Luigi. The UFO guides the Chomp towards a Bro. and the player has to quickly see which way the UFO is going. If two saucers are present she can ride on top of the UFO's and fire large energy blasts at the Bros. from the front; these come down much too fast for both Mario Bros. to jump over a blast at once, so they must pay attention to which hand the princess uses to fire the energy blast. The Princess will then fire at the Bros. from the background, forcing both Bros. to jump if the Princess isn't lined up with the top of her throne before being blown from the UFOs and landing on the platform, causing a shock-wave that again forces the Bros. to jump at the same time. With three UFOs she can summon a Shroob Meteor, with which she attempts to crush the Bros. Every time more Shroob UFOs are summoned, Princess Peach will throw a star to the Bros., with which they can knock saucers out of the sky and prevent Elder Princess Shroob from using some of her attacks.
The Princess's only move that is always available is a headlong football tackle towards one of the brothers. The younger versions of the plumbers then have to hammer her away multiple times before she finally relents, further, only the last strike counterattacks. Occasionally she will use a tactic of stopping right before the targeted brother, tricking him into swinging his hammer too early and then quickly charging again; she will reveal she is going to stop by waving her hand wildly and gaining a crooked expression. In the Japanese and European version of the game, every time after the player attacked Elder Princess Shroob, a ! appears above her and she would use this attack against the Bro. who attacked her, no matter whose turn it was.