マリオ&ルイージ RPG 2x2/ Mario & Luigi: Partners in Time

The famous Mario Brothers return in this sequel to the humorous Superstar Saga. In this adventure, Princess Peach takes a trip in a time machine, but when it returns, there's only a monster inside! The heroic brothers travel back in time only to discover that evil alien life forms known as the Shroobs have taken over the Mushroom Kingdom, and no-one is safe! They soon meet up with their younger selves, and set out to stop the alien menace, not to mention rescue the Princess!

When Professor E. Gadd unveils a time machine at Peach's Castle, Princess Peach travels into the past and never returns, and a hostile alien species called the Shroobs comes spilling through the rift. The Shroobs have overrun the Mushroom Kingdom of the past and taken Peach captive, so Mario and Luigi venture back through time to save her. There they meet their own infant selves, Baby Mario and Baby Luigi, and the four team up, combining the abilities of the grown brothers and the babies to solve puzzles, recover the scattered shards of the shattered Cobalt Star, and drive back the Shroob invasion.