Flashing Egg
A Flashing Egg is a very rare Yoshi Egg that has flashing spots that flash rapidly between red, pink, green and yellow, that it creates an illusion for the player, making it look brownish. Flashing Eggs appear in Super Mario World 2: Yoshi's Island and its remake Yoshi's Island: Super Mario Advance 3. Flashing Eggs were hard to find, and could not be gained by throwing an egg at a wall. Flashing Eggs could only be found on the ground in some areas. The reason why Flashing Eggs are so rare is because when a Flashing Egg hits an enemy, a Red Coin would appear from result of the impact. Flashing Eggs do not seem to have a Flashing Yoshi counterpart, and it is unknown who laid them and if they eventually hatch.
Flashing Eggs were not usable in Yoshi's Island DS, however, they made a cameo in an out of reach location in the final Secret Level of the game called "Yoshi's Island Easter Eggs".
Flashing Eggs return as a usable item in Yoshi's New Island.