How did she get this super power to increase in body size?
Born with it. Unnatural limit to squirrel stuffing.
What about Chubeko Koneko? Does she also have a super power that made her increase in body mass and size?
If someone pokes her, would it be like prodding those gold bars?
No. Her body acts as if it is that size. Its like a super power. You won't actually feel the gold bars.
Big and cute
I'm pretty sure that some people would gladly have this ability.
Ah yes, she can turn it all into muscle if she chose, yes?