The Jortshadow

In Super Mario Bros. 3, Bull's-Eye Bills (known as Missile Bills at the time of the game's release) appear in only one level, 4-5. They quickly flash between black and red; however, an obscure detail about them is that the red color during the flash will actually change to a different color depending on what character is being played, and what form that character is in. Please understand that no animations are provided due to rapid 1/60th-second flashing they exhibit in-game.

Top left: the regular color of the Bull's-Eye Bills, which they assume between flashes. Top middle: the color they flash if playing as Small Mario, Super Mario or Raccoon Mario. Top right: the color they flash if playing as Frog Mario, Frog Luigi, Small Luigi, Super Luigi, or Raccoon Luigi. Bottom left: the color they flash if playing as Fire Mario or Fire Luigi. Bottom middle: the color they flash if playing as Tanooki Mario or Tanooki Luigi.

Finally, in the bottom right is a form of the Bull's-Eye Bills that can never be seen during regular gameplay without cheating, that being the color they flash when playing as Hammer Mario or Hammer Luigi. As it is not possible to obtain a Hammer Suit in World 4 or earlier during regular gameplay, it cannot be seen without using cheats or glitches.