Princess Shroob is the main antagonist of Mario & Luigi: Partners in Time. She is the second-in-command of the alien race known as the Shroobs. As the primary antagonist of Mario & Luigi: Partners in Time, Princess Shroob is a militant conqueror and is shown to be highly demanding, always getting what she wants thanks to her Shroob servants. 

During her recent takeover of Earth however, she met a human. One who she was quite fond of. She offered to spare earth, so long as you were hers...