It has caught on in a manner : in the past number of years in southern California when temperatures are mild (for so. Calif.), I see many people wearing a sweatshirt (yet not a sweater) with short pants. I think the same is happening in other parts of the country or even other parts of the world when the weather is not too cold & not too hot.
If I made a comic, I would enjoy people discussing in detail about the characters &/or comic. It shows that there is a good story line & shows good character development.
I think he is wearing or those are his pajamas, not jeans.