Shadow-Play Alley

Shadow-Play Alley, also known as World 2-3, is the ninth regular level and the third course of World 2 in Super Mario 3D World and its Nintendo Switch port Super Mario 3D World + Bowser's Fury. It is an inside course with a part of it taking place in the shadows. It is unlocked along with World 2-2, Puffprod Peaks, by completing Conkdor Canyon, and completion of either this level or 2-2 unlocks Really Rolling Hills. Shadow-Play Alley also appears in the Wii U version of Captain Toad: Treasure Tracker as an extra stage if the player's Wii U has save data for Super Mario 3D World.

Layout
The course starts in an underground area with some Fuzzies and Piranha Plants. Some moving platforms and Fire Piranha Plants await, followed by the Checkpoint Flag. The next area is set in the shadows, where the player has to navigate through an area full of Fuzzies, Piranha Plants, and one Mega Piranha Plant until they reach the door leading them to another area. Here, the player must pass some enemies and moving platforms until they reach another door which leads them to the Goal Pole.

Green Stars

 * Green Star 1: Shown in the shadows at the very beginning of the level.
 * Green Star 2: Inside a Mystery Box guarded by Blurkers, the player has to hit the P-Switch to reveal a shadow of the Green Star.
 * Green Star 3: Before the door exit, there's a hidden gap that reveals Captain Toad scared by the shadow of a wooden cutout of Bowser. The player has to knock it down then Captain Toad will give the third Green Star.

Stamp

 * Under the ground during the shadow section, near the Big Piranha Plant (see picture above). To reach it, the player needs to be in Cat Form to claw the crates next to the Stamp and reach it. The stamp is a Piranha Plant.

Super Mario 3D World
The player needs to use the Cat Suit to climb up the wall at the beginning of the stage to find a shadow of a 8-bit Super Luigi sprite crouching in the top left corner.

Captain Toad: Treasure Tracker
An 8-bit Luigi can be seen in one of the tunnels by moving to the right and looking inside the tunnel.

Names in other languages
Unterirdische Schattenspiele