Challenge Node is a location inside Bowser's body that appears in Mario & Luigi: Bowser's Inside Story. The Challenge Node is a special place where Mario and Luigi must pay coins in order to fight stronger versions of previous, fought bosses for prizes. Mario and Luigi can also use their Special Attacks in this area as a challenge. The Challenge Node is located directly beside Toad Square and directly above the Flab Zone. The Challenge Node is the only area inside Bowser that does not need to be visited at any point in order to complete the game.