I exist! About cultural differences: Yes, there are plenty. But not only between Northern, Central, and Southern Italians. Literally every region was a separate kingdom and territory up until less than 200 years ago. People lived different lives, spoke different languages (more than just dialects, sometimes), ate different food, and had different traditions.
Literally from one village to the next, we locals already notice differences. Of course, when you look at the whole Country, the north/center/south differences are even more evident. Italians really love to hold on to those differences, for better or worse, as part of their identity, and it is a very interesting topic to explore.
As per stereotypes: I would never say that Southerners are lazier, or that Northerners are colder people, but of course, people still say that the weather & the food have a big influence on people's attitudes and cultures.