How do you get Sparkling Aniimo?

There is a third route the answer leaves out: the Sparkling Cube turns any wild Aniimo it catches into a Sparkling. That makes it the one method you control. Wild encounters and eggs are luck. The cube is a choice of target.

The cube is a rare capture device, so treat it as a limited resource rather than a pod you throw at everything. Because it works on any wild Aniimo, the sensible use is on a species you actually want to keep and field, not on whatever happens to be closest. The change it makes is to the creature's appearance.

For the other two routes, the practical advice is to keep catching and keep hatching. Rare eggs found in the wild are one of the named egg sources, so pick them up when you see them rather than walking past.

Is a Sparkling also a perfect Aniimo?

Being Sparkling is about how the creature looks. Its quality is a separate roll. Every captured Aniimo has a Potential grade, an Attribute Rank of Common, Good, Elite or Perfect, which sets its stat ceiling, and it shows as "Unappraised" until you submit the creature in a catch report at an Outpost's Research Console. Even a standard cube has a random chance of producing perfect stats. So appraise a new Sparkling the same way you would any other catch before deciding it is the one to build.

Sparkling vs Prismana

These are different things. Prismana Aniimo spawn during Prismana Flow, a weather event tied to a region's prismatic energy, and Lucky Strikes while catching can fill that energy bar to maximum and bring the regional Prismana Aniimo out immediately. A Super Lucky Strike also awards bonus credits and sparkling crystals. None of that turns a creature Sparkling; for that you need the wild, an egg or the Sparkling Cube. The Lucky Strikes article covers the energy side in full.