A Flashing Shell is an object in Super Mario World and its Game Boy Advance remake Super Mario World: Super Mario Advance 2.
Description[]
A Flashing Shell is a type of Koopa Shell that quickly alternates between several colors. It is created whenever a yellow Koopa without a Shell climbs into an empty shell of any color. A Flashing Shell attempts to hit Mario or Luigi by spinning around and dashing in his direction. A Koopa without a Shell cannot be ejected from a Flashing Shell.
Like with other Koopa Shells, the Flashing Shell can defeat enemies along the way, and even though a Flashing Shell cannot be shown, the player can still receive a combo in increasing point values for enemies successively defeated by a Flashing Shell and extra lives starting with the eighth enemy.
In Super Mario World[]
Flashing Shells first appear in Donut Plains 4. If Mario or Luigi jump onto a Flashing Shell, they bounce upward, but this does not destroy the Flashing Shell. A Flashing Shell can only be destroyed by either a Yoshi eating it, a Spin Jump, invincibility, or Caped Mario's Body Press maneuver. If a Yoshi eats a Flashing Shell, regardless of their color, he gains all three shell abilities—sand clouds, flying, and breathing fire—for as long as the Flashing Shell remains in his mouth.
During Fall, just like with other Koopa Shells, Flashing Shells are redesigned to resembles Mario's face, but in the case of Flashing Shells, it still quickly alternates between several colors.