"Mmhmm," Klaus answered the question. "Of course, I suppose that depends on people's definitions of maturity. I, for one, see nothing wrong or immature about a healthy sense of fun."

Granted, fine, his idea of fun was usually pretty destructive--or, at least some of his ideas of fun. Clearly, he had non-destructive ideas of fun, too. Like sketching and art and museums. Possibly hanging out with Jack met both "fun" impulses.