Sneaky Spirits, or White Apparition (しろいおばけ,Shiroi Obake?), are enemies from the Rhythm Heaven series, from the Rhythm Heaven mini-game White Apparition and its sequels/remakes. The point of the game is to fire arrows at incoming ghosts.
The Sneaky Spirits appear as enemies in the Smash Run mode. These rhythmic spooks pop up from the floor at regular intervals. Defeating one of these bonus enemies before they leave usually grants great rewards.
Skinny white ghosts that travel with a smirk on their face. They move like they do in Rhythm Heaven, popping up and down in rhythm before trying to run away. If you manage to defeat one, you'll earn a star-shaped stat boost that improves all of your stats. Time your attacks and keep them from escaping.