Mario and Luigi: Superstar Simulator focuses on the battle elements of the Mario and Luigi series and enhances them with new enemies to fight and characters to play as. The playable characters range from the usual such as Mario, Luigi, and Bowser, but there are also some characters you wouldn't expect in this format such as Paper Mario, Sonic, or even Peppino from Pizza Tower. Each battle has something special and unique to bring to the table, like a new mechanic while dodging or a phase 2 that changes things up. There are some extra things to do as well, like playing minigames or going on bounty missions by collecting wanted posters in the overworld/HUB area.