No, they can't. Otherwise, I would have Eclipse Ash Ketchum with an actual Pikachu that attacks with actual thunderbolts (yay storm mother spirit charms).
You don't actually have to use Eclipse-charms at all!
While they are listed under "Strange Folk and Monsters" and not under Animals, Mice of the Sun have entries for Latent and Magical abilities. Those are pretty flexible - you can explicitly create customized ones, or take ones listed under other animals.
One example would be "Aspect of the Garda", listed under Austrech:
"The Austrech's master may pay five motes to imbue it with the fiery-winged aspect of the Garda, causing it's feathers to become dancing sprays of flame. The austrech may use its movement action to fly through the air, and its fiery glory adds one automatic success to all attack rolls and one die to all damage rolls. These benefits last for one round. If the Austrech does not end it's movement on the ground, it's master may activate Aspect of the Garda again on the next round, or else the bird falls."
A clearly elemental aspect, and I'm sure there is a fire-landbird pokemon somewhere.
Better yet, there is Deadly Predator Method. It supercharges your familiar and explicitly makes non-combat ones combat-capable (given example is a Hummingbird). And you can create a special ability that can only be used during Deadly Predator Method, and they explicitly "need not be wholly appropriate for the animal in question". It lists teaching a flying squirrel to shoot lightnign as an example.
The only drawback is all that needs Essence 3 and that it only works with animals. Whether a Twilight can use it on spirit-familiars is not certain.
Oh, and you can create custom spirit-familiars with Ephemeral Induction Technique. It's Essence 5 and has a lot of prerequisite charms, but the familiar can look however you like and does of course learn charms.
Better yet, at least one Artifact (Orichalcum Hunting Hawk) has an Evocation where you create a familiar animal from it (a hawk, of course).
So yes, it's certainly possible to create "Exalted Ash Katchum".
Starting with a Mouse of the Sun as a familiar works very well. With either Supernal Survival or Essence 3, you can teach that mouse to throw lightning (or more appropriately, sunbeams).
The question is how to go about the other "pokemon". Normal animal-familiars don't work very well, since there is no method of sending them to pocket dimensions. A Twilights ability to make demons and elementals into familiars works, and with Supernal Occult you can even create an entirely custom familiar. Alternatively, you could get the help of your GM and create an artifact belt with Evocations. Have them work like Sun-Gilded Hawk Soul, but allow several such familiars to reside within the belt.
