Looks like a tomatillo.... Edit: Oops... My bad, I see that you've already labled it "physalis". I'd be interested in seeing the fruit that it sets...
Yes It must be Tomatillo. I did have some few years ago and I reuse some soil in this pot so a seed should have come back to the surface. The only weird thing is the size of the leaves. Some are really big (20 cm - 7 to 8 inches) I'll let you know.
