Mario & Luigi Superstar Saga series

Mario & Luigi: Superstar Saga
The first game in the series was Mario & Luigi: Superstar Saga, released in 2003 for the Game Boy Advance. In the game, two new villains, Cackletta and Fawful, steal Princess Peach's voice. Mario and Luigi jump into the action and travel to the Beanbean Kingdom to stop them. It is later found out that Cackletta had stolen Peach's voice to awaken the Beanstar, a powerful star that can grant all wishes, such as letting Cackletta rule the world, that is awakened by a pure voice. Princess Peach happened to be the one with the "pure" voice.

Mario & Luigi: Partners in Time
A sequel to Mario & Luigi: Superstar Saga was released for the Nintendo DS in 2005, called Mario & Luigi: Partners in Time. This game centers on the Mushroom Kingdom of the past, during the invasion of an alien race known as the Shroobs. Unaware of the danger, Princess Peach uses a time machine built by Professor E. Gadd to travel into the past, where she was promptly captured by the alien leader, Princess Shroob. Teaming up with Baby Mario and Baby Luigi, the adult Mario bros. set off to defeat the Shroobs and save Peach, using Time Holes created by the malfunctioning time machine to travel back and forth through time.

Mario & Luigi: Bowser's Inside Story
The third installment, Mario & Luigi: Bowser's Inside Story, was announced at Nintendo's Fall Press Conference on October 2nd, 2008 and released four months later. While Mario and Luigi are still playable, Bowser also becomes a central protagonist in this game as he attempts to reclaim both the Mushroom and Koopa Kingdoms from Fawful, who used an outbreak of a disease known as the Blorbs as an opportunity to launch his own evil plot for world domination. Fawful later gives Bowser a Vacuum Mushroom, making Bowser inhale everything around him, including Mario, Luigi, Princess Peach, and other characters.

Mario & Luigi: Dream Team
The fourth installment, Mario & Luigi: Dream Team, was announced during February 14, 2013's Nintendo Direct. Due to the shift to 3D, the game uses a new art style. In this game, Mario, Luigi, Princess Peach, and Toadsworth go on a trip to Pi'illo Island, where the bat king Antasma has turned many residents into stone, and kidnaps Peach. In order to save the Pi'illo Island folk and the princess, Mario must explore both the real, tridimensional world and the side-scrolling world in Luigi's dreams.