What actually happens to a Magical Child familiar's stats?

[Weirdo]

Animal Guide Ability:

A magical child starts play with a magical spirit guide in the form of a familiar, using her vigilante level as her effective wizard level. The familiar also has a social identity as a seemingly normal animal, though vigilantes with outlandish familiars might still need to hide the familiar.

At 3rd level, the magical child's familiar reveals another aspect of its form, and its vigilante identity changes into a creature on the Improved Familiar list that would be available to a 3rd-level spellcaster (the animal guide's social identity always remains as the original normal animal).

The familiar can change its vigilante identity again when the magical child reaches 5th and 7th level, each time to familiars available at those levels. The Improved Familiar feat's alignment restrictions apply to this ability, but only the magical child's vigilante identity needs to have an alignment that fulfills the alignment requirements of the improved familiar. The familiar's new vigilante form choices are permanent, and it cannot transform back into its former vigilante identities until 9th level, when the familiar gains the change shape universal monster ability if it doesn't already have it. It can use this ability at will when in its vigilante identity to transform into any of its four vigilante identities.

In vigilante form, a magical child's familiar gains an amount of DR/magic equal to her vigilante level. This doesn't stack with any DR/magic that her vigilante form might already possess.

Should each form have its own stats to match that of the appropriate Improved Familiar, complete with different feats, mental ability scores, languages, and non-master-derived skill ranks?

If the stats don't change entirely when the familiar changes shape, how do we decide what does change?

[Weirdo]

So we are all pretty clueless about this?

[CBDunkerson]

Yep. There are several very different opinions on how it works.

I prefer treating each form almost as a separate familiar. Just as they can be different creature types, have different alignments, and speak different languages... so too can they each have different familiar archetypes.

The only universals across form are memories and features derived from the bonded Vigilante.

[Weirdo]

That seems like the simplest way to do it, though I find it very weird that the familiar would have the same memories but different languages and skill points. (The different alignments are least consistent with the vigilante identities switching alignments around.)