Mario & Luigi: Partners in Time (known in Japan as Mario and Luigi RPG 2X2) is the second game in the Mario & Luigi series and the sequel to Mario and Luigi: Superstar Saga. Unlike Superstar Saga, this game had Baby Mario and Baby Luigi as playable characters, along with Mario and Luigi.
During the events of Partners in Time, Professor Elvin Gadd invents a time machine which Princess Peach travels through to see the Mushroom Kingdom's time. However, an alien race known as the Shroobs invade the kingdom's past and kidnap her. Later in the present time, Time Holes begin to pop up everywhere. Throughout the game, Mario and Luigi along with their baby selves travel through the holes to collect the Cobalt Star Shards.
- The name, Partners in Time is a pun on Partners in Crime.