Hello
a little while ago there was a comet festival that brought with it the Star dust effect,
The only pets that had the art for this effect were pets from Scira and a few CS pets.
To get this effect you need to use Piles of star dust
a Pile of Silver star dust= gives the star dust effect to Scira pets.
a Pile of Gold star dust = gives the star dust effect to CS pets.
You will have to use the piles of star dust with a Stardust urn
to make a Silver star dust urn
and/ or a Gold star dust urn.
you can then use it on the appropriate pet.
( this is how I remember it, terribly sorry if this is wrong and I hope it helped)
:)