Luigi may not have the larger role he claimed in the past three Paper Mario titles, but he does make five different cameos in each of the game’s five worlds (not including World 6). In each cameo, Mario can enter Paperize mode and pluck Luigi out right from the background. Removing Luigi from all five of the locations will result in his inclusion in the Character Parade during the credits.
Location #1 – World 1-6
On your way to the very first boss of the game, Luigi can be seen on the ledge while you are crossing the bridge to get into the tower. This Luigi cameo cannot be missed and will be passed as you play through the game.
Location #2 – World 2-5
This location can be missed! After draining the sand out of the third floor, head to the big doorway that leads to the fourth floor. Instead of entering, move to the right and enter the small hole in the wall. From this room, head outside and start moving right. Luigi will standing in the windowsill.
Location #3 – World 3-12
Looking out at the vast ocean from the pier in World 3-12 will reveal Luigi hanging around the distant rocks. This location will be passed twice in the game, so don’t miss it!
Location #4 – World 4-5
On the zip line, Luigi will temporarily pass by on the opposite line. Keep an eye out as he will only be on screen temporarily before moving on.
Location #5 – World 5-5
After falling through the hole to the ground that leads to the Cracked Boulder, move north and you should see a hot spring. Off to the left of the spring, Luigi will be relaxing within the misty atmosphere.