The YouTube page for this video simply says “no description available,” but is any really necessary? All you need to know is that this is a tiny Fiat 500 fitted with a 1200cc jar of hornets.
Here is another video of what I can only assume is the same car, doing some righteous autocrossing and sounding delicious doing it.

If you dig through the intergoogle machine, you’ll find that there are a lot (or more than just a few) of these 500/bike engine marriages around the world. Which isn’t surprising because it’s such an obvious idea. Why do motorcycle engines sound so good in cars?