Princess Shroob

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

Mario & Luigi: Partners in Time
Many years in the past, Princess Shroob invades the Mushroom Kingdom along with her sister 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 E. Gadd's Time Machine in its maiden voyage. Elder Princess Shroob personally attempts to capture her, but Peach reacts before they manage as much: she wields the Cobalt Star used to power the time machine, and it somehow imprisons Elder Princess Shroob before shattering, scattering across the Mushroom Kingdom. Following this setback, the younger Princess Shroob takes control of the invasion and manages to capture Peach. She sends a Junior Shrooboid into the time machine and sends to with the last of its power back to the future, where its appearance prompts the adult Mario Bros. to investigate the past via timeholes.

When the assembled past and present 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, aiming for the Koopa Cruiser. As the Koopa Cruiser was low on ammo, the missile easily hits the airship and leads to a crash landing in Baby Bowser's Castle.

Later on, when the Bros. storm the assembled Shroob army at the Koopaseum, Princess Shroob appears on stage to celebrate the conquest of the Mushroom Kingdom by feeding Princess Peach to Petey Piranha. The four heroes accost her, but Princess Shroob has the Shrooboid Brat fight them while she bears a retreat. Mario and company eventually defeat the Shrooboid Brat, only for Princess Shroob to have a hole broken under the heroes, where they fall into a cave and battle Petey Piranha.

Having beaten the Piranha Plant, Mario and company set out to rescue Peach in Gritzy Caves. When they reach her, she has a Shroob Mushroom attached to her face. They take her back to Princess Peach's Castle in the future. This princess was actually Princess Shroob, and her disguise fools everyone, even the adult Bowser, who kidnaps her believing she is Princess Peach. Bowser brings her to Thwomp Volcano, and after he is defeated by Mario and company, the Shroob Mother Ship arrives and captures the princess. Mario, Luigi, and their younger selves follow, still believing she is Princess Peach. Once they finally reach the fake Princess Peach, Princess Shroob reveals herself. She is poised to defeat them, but is suddenly blasted away by a disguised Kylie Koopa. The victory is short lived when Princess Shroob recovers and absorbs Mario and his friends into the bowels of the Shroob Mother Ship.

After conquering all the provinces infested with Shroobs and assembling the scattered shards of the Cobalt Star, the four Mario Bros. eventually make their way through a Shroobified Peach's Castle. At the top of the highest tower, the group hijacks a Shroob Battleship and engages the Shroob Princess aboard the Shroob Mother Ship in a dogfight. The brothers blast the Mother Ship from the sky; returning downstairs, they witness the Princess emerges from the wreckage. She is furious and almost incoherent, declaring Peach useless, the kingdom hers, and the brother's dooms sealed, shouting "Destroy!" repeatedly. The group enters battle.

Princess Shroob fights initially from the protection of her levitating throne, bearing a force field that can only be destroyed by repeatedly jumping. The force field does two attacks each turn and regenerates from disactivation after two turns. The force field can be destroyed or disabled easily with a Copy Flower. Princess Shroob fires laser beams of varying heights, challenging the brothers to anticipate and carefully alternate their dodging patterns. Princess Shroob also has an extended attack sequence that inflicts several status effects. The first part involves sprouting limbs from the throne, where she advances over a Mario bro. and fires laser rings directly downwards, which enclose from the outside, forcing rapid jumping to dodge. Failing to avoid this attack will cause damage and the trip status effect. After the laser barrage, Princess Shroob has her throne attempt to crush the brother directly. She will shake the mech three times and then either laugh or go straight down. If she laughs, the mech will delay before dropping. The attack can be countered by Hammer blows, and if unsuccessfully blocked will cause dizziness.

Once the brothers destroy her throne, the Shroob Princess employs personal attacks. She always teleports wildly before acting. 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's arm gestures telegraph which brother needs to dodge, either by jump or hammer. All her energy ball attacks can inflict Poison. Princess Shroob's final and most powerful attack is to launcing an energy Star that encircles the arena, travelling faster and faster until it strikes a brother, which can cause random stat decrease, or is stomped on. It can alter its speed to catch the group off-guard. If she points straight forward, the star will first attack Mario; if she points downwards, it attacks Luigi. Once Princess Shroob has lost half of her health, she begins to glow red, attacking more frequently and with more power. Eventually the four brothers triumph. Princess Shroob lies battered on the floor, near-death. Baby Bowser meanwhile assembles the Cobalt Star using the last piece. As the star suddenly starts to shudder ominously, the younger Shroob monarch she crawls to the Mario bros and shouts that it is her sister's turn to defeat them now. She then dies in a characteristic boss fight shower of sparks, as her elder sister at last breaks free from her prison.

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

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.

Powers and abilities
Princess Shroob is a formidable foe. Her source of power is unknown, though she demonstrates various energy abilities. Among those enable Princess Shroob to throw energy balls, fly, teleport, and control stars. Princess Shroob also shows technological skills via the use of her throne. She also seems to be a great master (or in her case, mistress) of disguise as she had everyone fooled into making her think she was the real Princess Peach.

Personality
The Princess is shown to have a vindictive, sadistic personality and takes joy in the pain of others, as shown when she laughs when the Koopa Cruiser is shot down and how she mercilessly feeds Princess Peach to Petey Piranha (though feeding the Princess to the monstrous Piranha Plant could have been just for show, as she had Peach spat back up, meaning she saw usefulness in the Princess). She kept Peach unharmed for the majority of the game because she needed her in order to take over the Mushroom Kingdom in the future, and even destroy the Mario bros (And possibly because she believed Peach knew where the Last Cobalt Shard was). She seems to have a vengeful side, as when Mario, Luigi, and their infant selves destroyed her Mothership, Princess Shroob grew insane and attacked in hopes of destroying them. Although she has a big sister who cares about her, she didn't seem to bother looking for the Cobalt shards, nor showed any indication that she intended to do so, though it's possible she had them guarded and wanted to wait until the Kingdom was fully conquered before freeing her sister.

Quotes (all in Shroob language)

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