Why does my pet cast electric shocks?

This is a screenshot of my pet (a former cat, now permanently transmogrified into a Mimic) shortly after triggering an outburst of lightning.

Please note that:

• My character is not doing anything.
• Mimics, as far as I know, do not cast electric shocks (feel free to correct me if I'm wrong).
• According to the Pet sheet, my pet inflicts zero elemental damage.

I don't know much about the inner workings of Torchlight, but I suspect a few factors:

• My pet has an amulet equipped which increases its electric damage by 3%.
• My currently equipped weapon inflicts electric damage.
• My pet was a Burrower at some point, and Burrowers do cast electric shocks.

Which one(s) is it?