Princess Shroob

Princess Shroob is the main antagonist of Mario & Luigi: Partners in Time. She is second-in-command of the alien race known as the Shroobs (her older twin sister is the leader), although initially it appears that she is their leader, since the elder Princess Shroob was absent, trapped in the Cobalt Star by Princess Peach. She and her sister set off a full invasion of the Mushroom Kingdom to make it their own.

Mario & Luigi: Partners in Time
Princess Shroob invades the Mushroom Kingdom in the past along with her sister, the Elder Princess Shroob, as their home world was withering. After the Shroobs take hold of Peach's Castle, they find the adult Princess Peach, who had just used Prof. E. Gadd's time machine to visit the past castle. The Elder Princess Shroob attempts to capture her, but Peach uses the Cobalt Star that powered the time machine to imprison the Elder Princess Shroob before it shatters, scattering the shards across the Mushroom Kingdom. The younger Princess Shroob then ambushes and captures Peach. She sends a Junior Shrooboid into the future using the last of the time machine's power back to the future, where its appearance prompts the adult Mario and Luigi to investigate the past via timeholes.

As the assembled baby and adult Mario Bros. ride aboard Baby Bowser's Koopa Cruiser, Princess Shroob is seen in a transmission, largely obscured by shadows. From the newly converted Shroob Castle, she fires a Shroob missile at the Koopa Cruiser, which was too low on ammo to shoot it down; the missile strikes the Cruiser and leads to a crash landing in Baby Bowser's Castle.

Later on, when the Mario Bros. enter the Koopaseum, Princess Shroob appears on stage, in the process feeding Princess Peach to Petey Piranha. Princess Shroob then sends the Shrooboid Brat to fight the Bros. while she retreats; the quartet defeats the Shrooboid Brat, only for Princess Shroob to have a hole broken under them, where they fall into Gritzy Caves.

After encountering and defeating Petey Piranha, the Mario Bros. find Peach, who has a Shroob mushroom attached to her face - unbeknownst to them, she is actually Princess Shroob in disguise. They take her back to Princess Peach's Castle in the future, where the adult Bowser arrives to kidnap her, unknowingly saving the present Peach's Castle from domination by the Shroobs. Bowser brings her to Thwomp Volcano, where he is later fought and defeated by the Mario Bros.; the Shroob Mother Ship arrives and captures the disguised Princess Peach, with the Mario Bros. in pursuit, and Princess Shroob finally reveals herself once they find her. As she and the Shroobs are poised to defeat them, she is suddenly blasted away by a disguised Kylie Koopa, who is eventually left on Yoshi's Island, while the Bros. are dropped into Toad Town.

After the Mario Bros. assemble the rest of the scattered shards of the Cobalt Star, they eventually go through a Shroobified Peach's Castle. At the top of the highest tower, they hijack a Shroob Battleship and engage Princess Shroob aboard the Shroob Mother Ship, eventually downing it. After they return downstairs to examine the wreckage alongside Princess Peach, a furious Princess Shroob descends from the wreckage on a floating throne, declaring Peach useless and moving to finish the group off and take over the kingdom, shouting "Destroy!" as the Bros. prepare to battle her.

Upon defeating her, Princess Shroob lies battered on the floor as Princess Peach and the quartet of Mario Bros. spot the almost-whole Cobalt Star floating into the room. Princess Peach reveals that she has the final shard, and that she cannot let it be reassembled, confusing the adult Mario Bros.; Baby Bowser suddenly ambushes the group and snatches the shard, assembling the Cobalt Star despite Peach's protests. Princess Shroob then crawls into view, shouting that it is her sister's turn to defeat them now before her eyes go dim and she dies in a burst of sparks; the Cobalt Star then begins darting around the room before turning Baby Bowser into a Shroob Mushroom, and Princess Peach reveals the truth about the Star just before Elder Princess Shroob regains her true form.

Battle
Princess Shroob starts the fight in her levitating throne, with a force field that can be destroyed by jumping attacks; the force field is used for attacks twice each turn, firing laser beams of varying heights. Shroob can also attack using mechanical limbs sprouting from the underside of throne as she advances over a pair of brothers, firing laser rings directly downwards that enclose them from the outside; the targets can dodge this attack by jumping over each ring, and being hit may inflict the Tripped status. After the laser barrage, Princess Shroob uses the throne to try and crush the brothers directly, with the throne rising up and down three times before dropping onto the target pair; if she laughs afterward, the mech delays before dropping. The attack must be countered by the Hammer, and being hit can render the target Dizzy.

Once the Mario Bros. disable her forcefield, the throne is also disabled and re-activates after two turns, forcing Princess Shroob to attack more directly. During this phase, she uses a different set of attacks, teleporting around the arena while firing energy blasts at the Bros., with her arm gestures telegraphing which brother is the target; if she points straight forward, the star first attacks Mario; if she points downwards, it attacks Luigi. She can shoot a lone fast energy ball at one brother, stand in the middle of the room and shoot a storm of energy balls, or hover in the air and rain energy balls downwards; Princess Shroob can also launch an energy Star that encircles the arena, traveling faster and faster until it strikes a brother, which can cause random stat decreases, or is stomped on. It can also alter its speed to catch the group off-guard.

All of her energy ball attacks can inflict Poison if they hit, and can be safely stomped on; the overhead energy ball must be countered with the hammer, while all the other types can be dodged by jumping, with the energy ball storm requiring each pair to jump one after the other. Once Princess Shroob has lost half of her health, she begins to glow red, attacking more frequently and with more power.

Mario & Luigi: Bowser's Inside Story + Bowser Jr.'s Journey
Princess Shroob makes a cameo appearance next to the Elder Princess Shroob during the optional boss fight of the Shroobs in Bowser's Castle, unlike in the original game, only the Elder Princess Shroob is barely seen. Princess Shroob is also mentioned in the Shroobs' profile from the Bowser Jr.'s Journey mode.

Super Mario-kun
Princess Shroob appears in the Mario & Luigi: Partners in Time adaptions in the Super Mario-kun manga, serving the same role as she does in the game.

Super Smash Bros. Ultimate
Princess Shroob appears as an Advanced-level, neutral spirit in Super Smash Bros. Ultimate. The battle to unlock the Princess Shroob spirit is a stamina battle against Princess Peach. After taking a high amount of damage, Peach becomes giant and her attack power increases, which is possibly to act as a reference to her older twin.

Powers and abilities
As the commander of the Shroobs and one of the final bosses of Mario & Luigi: Partners in Time, Princess Shroob is powerful and she often uses the Shroob army to her needs. By herself, she demonstrates various energy abilities, such as throwing energy balls, flying, and controling stars in her boss battle. Princess Shroob also shows technological skills via the use of her throne. In addition, she can disguise herself as Princess Peach to fool the characters, despite the disguise having a Shroob mushroom on her face.

Personality
As the primary antagonist of Mario & Luigi: Partners in Time, Princess Shroob is a militant conqueror and is shown to be highly aggressive (e.g., shooting down the Koopa Cruiser), though her dialogue is mostly undecipherable. In addition, the Shroob race acts as her loyal subordinates, serving her drinks and always following her commands. (It is hinted that she is her people’s source of corruption, though her sister may have played a part as well.) She also takes revenge on Peach for capturing her twin sister and imprisoning her in the Cobalt Star by capturing her, then planning on feeding Peach to Petey Piranha in front of a Shroob audience.

It is not entirely confirmed whether or not she cares for her older sister, as she did not attempt to rebuild the Cobalt Star and she referred to the Mushroom Kingdom as belonging to hers rather than her sister's.

Quotes
While Princess Shroob mainly speaks in the Shroob language, the quotes below are her lines translated in-game:


 * "I am Princess Shroob. You interlopers...will be consumed."
 * "NOW YOU'VE DONE IT!"
 * "YOU'RE USELESS NOW, PEACH!"
 * "TIME TO FINISH YOU!"
 * "YOU CANNOT ESCAPE! THIS KINGDOM IS MINE!"
 * "I WILL DESTROY YOU ALL! DESTROY!"
 * "NOW IT'S YOUR TURN... SIS... TER!"

Trivia

 * In the North American version, when the player defeats Princess Shroob, the victory screen appears showing that no Experience Points or coins are awarded. In other versions, the battle screen immediately fades out to the field after the death animation.
 * She is considered one of Mario’s most evil villains for her terrible cruelty towards the races of the Mushroom Kingdom, and the likely manipulation of her own people.