I'm raising the last of eight kids in a remote rural town, where the kids don't have a clue who Wally and the beav were. They embrace everything on tv and are very much part of the modern culture. As for the genre of the OPs son, my daughter called him an "emo". I don't have a clue as to what or why.
Yea, emo would at least potentially explain the nirvana shirt... Though of he were emo he might get really defensive about not being emo when you called him emo... (Emo= emotional)