List of Luigi sightings in New Super Luigi U

In every course of New Super Luigi U is a picture of Luigi hidden, whether it be a sprite, a image in a wall, or otherwise.

Soda Jungle
5-2 Dancing Blocks, Poison Swamp A Luigi sprite can be seen clinging to the top of the secret flagpole.

5-Ghost House Boo's Favorite Haunt

 * There is a portrait of Luigi to the right of the door leading to the secret exit.

6-1 Mount Fuzzy

 * Above the 1st Star Coin is a secret area with an 8-bit Luigi.

6-2 Porcu-Puffer Cavern

 * Next to the 2nd Star Coin is an 8-bit Luigi climbing a rope.

6-Tower Smashing-Stone Tower

 * In the area where the second Star Coin is.

6-5 Rising Piranhas

 * There is a large Luigi-shaped hole in the rock wall just before the Super Piranha Plant next to the secret exit in the ceiling.

7-3 Rainbow Skywalk

 * In the secret area before the end of the level, a large jumping 8-bit Luigi can be seen.

7-Ghost House Vanishing Ghost House

 * If the player takes the secret exit route, they will see a picture of King Boo and Luigi, which references their artwork from Luigi's Mansion: Dark Moon.

7-5 Flame Chomp Ferris Wheel

 * A cloud resembling Luigi can be seen in the background.

8-1 Magma Moat

 * There is a statue of Luigi taking off his hat at the secret flagpole.

The Final Battle

 * Luigi's face can be seen on the middle rivet of a platform.