This is an event Ponyta that was only available to be obtained through a event called AYE, SIR (more commonly referred to as ayesir). I was possible to get in many colors (pink, green, yellow, blue, purple, and rainbow). There was a 1 in 450 chance of finding them in the map and they have a 1 in 3 chance of being shiny (so 2/1350 chance of normal and 1/1350 chance of shiny).
They can be Everstone bred at a 2% success rate when you own an Egg Scope (1% otherwise). The child will have the same color as the parent Ponyta. Shiny cotton candy Ponyta can be used to breed with BrightPowder.
They evolve into Rainbow Rapidash starting at level 40.