Here at the Globizen Group we have a thing for small houses and we'd love to see more of them in Toronto. Constraints force creativity and we often don't need as much space and as many things as we think we do.
Here's an example from, not surprisingly, Japan (Osaka). It's called The Kakko House.
The lot size is 11.1' wide x 42.6' deep, or about 473 square feet. That's about the size of a studio apartment in Toronto. And this yet this home has a ground floor car park, 6 levels, and total of 1,216 sf.
That equates to a floor space index of about 2.57 (total building area divided by the size of the lot). As a comparison, here in Toronto, most residential areas have a maximum floor space index of 0.6 to, maybe, 1.0.
Canada has a bit more land to work with compared to Japan. But still.
For more photos, check out Design Milk. The above photos are from there via Yoshihiro Yamamoto Architects Atelier.